diff --git a/Cabal-syntax/src/Distribution/Version.hs b/Cabal-syntax/src/Distribution/Version.hs
index 2abf88100a8..a53a85b80fb 100644
--- a/Cabal-syntax/src/Distribution/Version.hs
+++ b/Cabal-syntax/src/Distribution/Version.hs
@@ -108,9 +108,13 @@ import Distribution.Types.VersionRange
 -- | This is the converse of 'isAnyVersion'. It check if the version range is
 -- empty, if there is no possible version that satisfies the version range.
 --
--- For example this is @True@ (for all @v@):
+-- For example, @\<v && >v@ is no version for all @v@.
 --
--- > isNoVersion (EarlierVersion v `IntersectVersionRanges` LaterVersion v)
+-- >>> ordNub [isNoVersion (earlierVersion v `intersectVersionRanges` laterVersion v) | v <- mkVersion <$> [[0],[1]]]
+-- [True]
+--
+-- >>> isNoVersion <$> [noVersion, anyVersion]
+-- [True,False]
 isNoVersion :: VersionRange -> Bool
 isNoVersion vr = case asVersionIntervals vr of
   [] -> True
@@ -118,8 +122,11 @@ isNoVersion vr = case asVersionIntervals vr of
 
 -- | Is this version range in fact just a specific version?
 --
--- For example the version range @\">= 3 && <= 3\"@ contains only the version
+-- For example the version range @\>= 3 && <= 3@ contains only the version
 -- @3@.
+--
+-- >>> isSpecificVersion (orLaterVersion (mkVersion [3]) `intersectVersionRanges` orEarlierVersion (mkVersion [3]))
+-- Just (mkVersion [3])
 isSpecificVersion :: VersionRange -> Maybe Version
 isSpecificVersion vr = case asVersionIntervals vr of
   [VersionInterval (LowerBound v InclusiveBound) (UpperBound v' InclusiveBound)]
@@ -222,5 +229,6 @@ transformCaretLower = hyloVersionRange embed projectVersionRange
 -- >>> :set -XScopedTypeVariables
 -- >>> import Distribution.Parsec
 -- >>> import Distribution.Pretty
+-- >>> import Distribution.Utils.Generic (ordNub)
 -- >>>
 -- >>> mapVR f xs = [pretty $ f v| Just v <- simpleParsec <$> xs]
diff --git a/cabal-install-solver/src/Distribution/Solver/Modular/Message.hs b/cabal-install-solver/src/Distribution/Solver/Modular/Message.hs
index 1b6fa0b3af5..16a1b1ff13b 100644
--- a/cabal-install-solver/src/Distribution/Solver/Modular/Message.hs
+++ b/cabal-install-solver/src/Distribution/Solver/Modular/Message.hs
@@ -309,7 +309,7 @@ showFR _ (PackageRequiresMissingComponent qpn comp) = " (requires " ++ showExpos
 showFR _ (PackageRequiresPrivateComponent qpn comp) = " (requires " ++ showExposedComponent comp ++ " from " ++ showQPN qpn ++ ", but the component is private)"
 showFR _ (PackageRequiresUnbuildableComponent qpn comp) = " (requires " ++ showExposedComponent comp ++ " from " ++ showQPN qpn ++ ", but the component is not buildable in the current environment)"
 showFR _ CannotReinstall                  = " (avoiding to reinstall a package with same version but new dependencies)"
-showFR _ NotExplicit                      = " (not a user-provided goal nor mentioned as a constraint, but reject-unconstrained-dependencies was set)"
+showFR _ NotExplicit                      = " (not a user-provided goal nor mentioned as a constraint when reject-unconstrained-dependencies=all)"
 showFR _ Shadowed                         = " (shadowed by another installed package with same version)"
 showFR _ (Broken u)                       = " (package is broken, missing dependency " ++ prettyShow u ++ ")"
 showFR _ UnknownPackage                   = " (unknown package)"
diff --git a/cabal-install-solver/src/Distribution/Solver/Modular/Solver.hs b/cabal-install-solver/src/Distribution/Solver/Modular/Solver.hs
index cb9b204b5cb..f2197379076 100644
--- a/cabal-install-solver/src/Distribution/Solver/Modular/Solver.hs
+++ b/cabal-install-solver/src/Distribution/Solver/Modular/Solver.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE ViewPatterns #-}
 #ifdef DEBUG_TRACETREE
 {-# OPTIONS_GHC -Wno-orphans #-}
 #endif
@@ -18,6 +19,7 @@ import Distribution.Verbosity
 
 import Distribution.Compiler (CompilerInfo)
 
+import Distribution.Version
 import Distribution.Solver.Types.PackagePath
 import Distribution.Solver.Types.PackagePreferences
 import Distribution.Solver.Types.PkgConfigDb (PkgConfigDb)
@@ -41,6 +43,7 @@ import Distribution.Solver.Modular.PSQ (PSQ)
 import Distribution.Solver.Modular.RetryLog
 import Distribution.Solver.Modular.Tree
 import qualified Distribution.Solver.Modular.PSQ as PSQ
+import Distribution.Solver.Types.PackageConstraint
 
 import Distribution.Simple.Setup (BooleanFlag(..))
 
@@ -140,15 +143,13 @@ solve sc cinfo idx pkgConfigDB userPrefs userConstraints userGoals =
     prunePhase       = (if asBool (avoidReinstalls sc) then P.avoidReinstalls (const True) else id) .
                        (case onlyConstrained sc of
                           OnlyConstrainedAll ->
-                            P.onlyConstrained pkgIsExplicit
+                            P.onlyConstrained (`S.member` versionConstrainedOrGoals)
                           OnlyConstrainedNone ->
                             id)
     buildPhase       = buildTree idx (independentGoals sc) (S.toList userGoals)
 
-    allExplicit = M.keysSet userConstraints `S.union` userGoals
-
-    pkgIsExplicit :: PN -> Bool
-    pkgIsExplicit pn = S.member pn allExplicit
+    versionConstrained = filterVersion isVersionConstrained userConstraints
+    versionConstrainedOrGoals = versionConstrained `S.union` userGoals
 
     -- When --reorder-goals is set, we use preferReallyEasyGoalChoices, which
     -- prefers (keeps) goals only if the have 0 or 1 enabled choice.
@@ -166,6 +167,25 @@ solve sc cinfo idx pkgConfigDB userPrefs userConstraints userGoals =
       | asBool (reorderGoals sc) = P.preferReallyEasyGoalChoices
       | otherwise                = id {- P.firstGoal -}
 
+-- | Keep package names of constraints that satisfy the predicate.
+filterVersion :: (LabeledPackageConstraint -> Bool) -> M.Map PN [LabeledPackageConstraint] -> Set PN
+filterVersion versionFilter = M.keysSet . M.filter (not . null) . M.map (filter versionFilter)
+
+normalise :: VersionRange -> VersionRange
+normalise = fromVersionIntervals . toVersionIntervals
+
+-- | Unconstrained with a version range @>=0@ or @<0@ or their flag equivalents
+-- and constrained by other versions ranges.
+--
+-- Both the @-any@ and @-none@ flags are considered unconstrained, because they
+-- don't actually constrain the version of the package. The @-any@ flag allows
+-- any version, and the @-none@ flag effectively excludes a package.
+isVersionConstrained :: LabeledPackageConstraint -> Bool
+isVersionConstrained (LabeledPackageConstraint (PackageConstraint _ c) _) = case c of
+    PackagePropertyVersion (normalise -> vr) -> not (isAnyVersion vr || isNoVersion vr)
+    -- `PackagePropertyFlags` @-any@ and @-none@ are covered below.
+    _ -> False
+
 -- | Dump solver tree to a file (in debugging mode)
 --
 -- This only does something if the @debug-tracetree@ configure argument was
diff --git a/cabal-install/tests/UnitTests/Distribution/Solver/Modular/Solver.hs b/cabal-install/tests/UnitTests/Distribution/Solver/Modular/Solver.hs
index b3780e2a345..d76928e982f 100644
--- a/cabal-install/tests/UnitTests/Distribution/Solver/Modular/Solver.hs
+++ b/cabal-install/tests/UnitTests/Distribution/Solver/Modular/Solver.hs
@@ -242,33 +242,117 @@ tests =
             mkTest dbBaseOld "Refuse to install very old base" ["base"] $
               solverFailure (isInfixOf "rejecting: base-1 (constraint from non-reinstallable package requires >=4.22)")
       ]
-  , testGroup
+  , -- reject-unconstrained-dependencies=all requires all non-goals to be
+    -- version constrained. Goals don't need constraints and flag constraints
+    -- are not enough.
+    testGroup
       "reject-unconstrained"
-      [ runTest $
-          onlyConstrained $
-            mkTest db12 "missing syb" ["E"] $
-              solverFailure (isInfixOf "not a user-provided goal")
-      , runTest $
-          onlyConstrained $
-            mkTest db12 "all goals" ["E", "syb"] $
-              solverSuccess [("E", 1), ("syb", 2)]
-      , runTest $
-          onlyConstrained $
-            mkTest db17 "backtracking" ["A", "B"] $
-              solverSuccess [("A", 2), ("B", 1)]
-      , runTest $
-          onlyConstrained $
-            mkTest db17 "failure message" ["A"] $
-              solverFailure $
-                isInfixOf $
-                  "Could not resolve dependencies:\n"
-                    ++ "[__0] trying: A-3 (user goal)\n"
-                    ++ "[__1] next goal: C (dependency of A)\n"
-                    ++ "[__1] fail (not a user-provided goal nor mentioned as a constraint, "
-                    ++ "but reject-unconstrained-dependencies was set)\n"
-                    ++ "[__1] fail (backjumping, conflict set: A, C)\n"
-                    ++ "After searching the rest of the dependency tree exhaustively, "
-                    ++ "these were the goals I've had most trouble fulfilling: A, C, B"
+      [ testGroup
+          "[A, B]"
+          [ runTest $
+              onlyConstrained $
+                mkTest db17 "accept backtracking finds all goals closed set" ["A", "B"] $
+                  solverSuccess [("A", 2), ("B", 1)]
+          , runTest $
+              constraints [ExVersionConstraint (ScopeAnyQualifier "B") (V.thisVersion (V.mkVersion [1]))] $
+                onlyConstrained $
+                  mkTest db17 "accept non-goal 'B' version-constrained" ["A"] $
+                    solverSuccess [("A", 2), ("B", 1)]
+          , runTest $
+              constraints [ExFlagConstraint (ScopeAnyQualifier "B") "flag" False] $
+                onlyConstrained $
+                  mkTest db17 "reject non-goal 'B' flag-constrained" ["A", "C"] $
+                    solverFailure $
+                      isInfixOf
+                        "Could not resolve dependencies:\n\
+                        \[__0] trying: C-1 (user goal)\n\
+                        \[__1] next goal: B (dependency of C)\n\
+                        \[__1] fail (not a user-provided goal nor mentioned as a constraint when reject-unconstrained-dependencies=all)\n\
+                        \[__1] fail (backjumping, conflict set: B, C)\n\
+                        \After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: C, B"
+          , runTest $
+              onlyConstrained $
+                mkTest db17 "reject non-goal 'C' unconstrained" ["A"] $
+                  solverFailure $
+                    isInfixOf
+                      "Could not resolve dependencies:\n\
+                      \[__0] trying: A-3 (user goal)\n\
+                      \[__1] next goal: C (dependency of A)\n\
+                      \[__1] fail (not a user-provided goal nor mentioned as a constraint when reject-unconstrained-dependencies=all)\n\
+                      \[__1] fail (backjumping, conflict set: A, C)\n\
+                      \After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: A, C, B"
+          ]
+      , testGroup
+          "[base, syb, E]"
+          [ runTest $
+              onlyConstrained $
+                mkTest db12 "accept all goals, no other dependencies" ["base", "E", "syb"] $
+                  solverSuccess [("E", 1), ("syb", 2)]
+          , runTest $
+              constraints [ExVersionConstraint (ScopeAnyQualifier "base") (V.thisVersion (V.mkVersion [4]))] $
+                onlyConstrained $
+                  mkTest db12 "accept non-goal 'base' version-constrained" ["E", "syb"] $
+                    solverSuccess [("E", 1), ("syb", 2)]
+          , runTest $
+              constraints [ExVersionConstraint (ScopeAnyQualifier "syb") (V.thisVersion (V.mkVersion [2]))] $
+                onlyConstrained $
+                  mkTest db12 "accept non-goal 'syb' version-constrained" ["base", "E"] $
+                    solverSuccess [("E", 1), ("syb", 2)]
+          , runTest
+              $ constraints
+                [ ExVersionConstraint (ScopeAnyQualifier "base") (V.thisVersion (V.mkVersion [4]))
+                , ExVersionConstraint (ScopeAnyQualifier "syb") (V.thisVersion (V.mkVersion [2]))
+                ]
+              $ onlyConstrained
+              $ mkTest db12 "accept non-goals 'base' and 'syb' version-unconstrained" ["E"]
+              $ solverSuccess [("E", 1), ("syb", 2)]
+          , runTest $
+              onlyConstrained $
+                mkTest db12 "reject non-goal 'base' unconstrained" ["E", "syb"] $
+                  solverFailure $
+                    isInfixOf
+                      "Could not resolve dependencies:\n\
+                      \[__0] trying: E-1 (user goal)\n\
+                      \[__1] next goal: E.base (dependency of E)\n\
+                      \[__1] fail (not a user-provided goal nor mentioned as a constraint when reject-unconstrained-dependencies=all)\n\
+                      \[__1] fail (backjumping, conflict set: E, E.base)\n\
+                      \After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: E, E.base"
+          , runTest $
+              onlyConstrained $
+                mkTest db12 "reject non-goal 'syb' unconstrained" ["base", "E"] $
+                  solverFailure $
+                    isInfixOf
+                      "Could not resolve dependencies:\n\
+                      \[__0] trying: E-1 (user goal)\n\
+                      \[__1] next goal: syb (dependency of E)\n\
+                      \[__1] fail (not a user-provided goal nor mentioned as a constraint when reject-unconstrained-dependencies=all)\n\
+                      \[__1] fail (backjumping, conflict set: E, syb)\n\
+                      \After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: E, syb"
+          , runTest $
+              constraints [ExFlagConstraint (ScopeAnyQualifier "base") "flag" True] $
+                onlyConstrained $
+                  mkTest db12 "reject non-goal 'base' only flag-constrained" ["E", "syb"] $
+                    solverFailure $
+                      isInfixOf
+                        "Could not resolve dependencies:\n\
+                        \[__0] trying: E-1 (user goal)\n\
+                        \[__1] next goal: E.base (dependency of E)\n\
+                        \[__1] fail (not a user-provided goal nor mentioned as a constraint when reject-unconstrained-dependencies=all)\n\
+                        \[__1] fail (backjumping, conflict set: E, E.base)\n\
+                        \After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: E, E.base"
+          , runTest $
+              constraints [ExStanzaConstraint (ScopeAnyQualifier "base") [TestStanzas]] $
+                onlyConstrained $
+                  mkTest db12 "reject non-goal 'base' only stanza-constrained" ["E", "syb"] $
+                    solverFailure $
+                      isInfixOf
+                        "Could not resolve dependencies:\n\
+                        \[__0] trying: E-1 (user goal)\n\
+                        \[__1] next goal: E.base (dependency of E)\n\
+                        \[__1] fail (not a user-provided goal nor mentioned as a constraint when reject-unconstrained-dependencies=all)\n\
+                        \[__1] fail (backjumping, conflict set: E, E.base)\n\
+                        \After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: E, E.base"
+          ]
       ]
   , testGroup
       "Cycles"
diff --git a/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/a.cabal b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/a.cabal
new file mode 100644
index 00000000000..5d9797ccf7d
--- /dev/null
+++ b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/a.cabal
@@ -0,0 +1,7 @@
+cabal-version: 2.2
+name: a
+version: 0
+
+library
+  build-depends:
+    some-lib
diff --git a/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.any-flag.out b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.any-flag.out
new file mode 100644
index 00000000000..49872a08df4
--- /dev/null
+++ b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.any-flag.out
@@ -0,0 +1,14 @@
+# tar
+# tar
+# tar
+# cabal v2-update
+Downloading the latest package list from test-local-repo
+# cabal v2-build
+Resolving dependencies...
+Error: [Cabal-7107]
+Could not resolve dependencies:
+[__0] trying: a-0 (user goal)
+[__1] next goal: some-lib (dependency of a)
+[__1] fail (not a user-provided goal nor mentioned as a constraint when reject-unconstrained-dependencies=all)
+[__1] fail (backjumping, conflict set: a, some-lib)
+After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: a (2), some-lib (1)
diff --git a/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.any-version.out b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.any-version.out
new file mode 100644
index 00000000000..49872a08df4
--- /dev/null
+++ b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.any-version.out
@@ -0,0 +1,14 @@
+# tar
+# tar
+# tar
+# cabal v2-update
+Downloading the latest package list from test-local-repo
+# cabal v2-build
+Resolving dependencies...
+Error: [Cabal-7107]
+Could not resolve dependencies:
+[__0] trying: a-0 (user goal)
+[__1] next goal: some-lib (dependency of a)
+[__1] fail (not a user-provided goal nor mentioned as a constraint when reject-unconstrained-dependencies=all)
+[__1] fail (backjumping, conflict set: a, some-lib)
+After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: a (2), some-lib (1)
diff --git a/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.none-flag.out b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.none-flag.out
new file mode 100644
index 00000000000..49872a08df4
--- /dev/null
+++ b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.none-flag.out
@@ -0,0 +1,14 @@
+# tar
+# tar
+# tar
+# cabal v2-update
+Downloading the latest package list from test-local-repo
+# cabal v2-build
+Resolving dependencies...
+Error: [Cabal-7107]
+Could not resolve dependencies:
+[__0] trying: a-0 (user goal)
+[__1] next goal: some-lib (dependency of a)
+[__1] fail (not a user-provided goal nor mentioned as a constraint when reject-unconstrained-dependencies=all)
+[__1] fail (backjumping, conflict set: a, some-lib)
+After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: a (2), some-lib (1)
diff --git a/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.none-version.out b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.none-version.out
new file mode 100644
index 00000000000..49872a08df4
--- /dev/null
+++ b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.none-version.out
@@ -0,0 +1,14 @@
+# tar
+# tar
+# tar
+# cabal v2-update
+Downloading the latest package list from test-local-repo
+# cabal v2-build
+Resolving dependencies...
+Error: [Cabal-7107]
+Could not resolve dependencies:
+[__0] trying: a-0 (user goal)
+[__1] next goal: some-lib (dependency of a)
+[__1] fail (not a user-provided goal nor mentioned as a constraint when reject-unconstrained-dependencies=all)
+[__1] fail (backjumping, conflict set: a, some-lib)
+After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: a (2), some-lib (1)
diff --git a/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.out b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.out
new file mode 100644
index 00000000000..49872a08df4
--- /dev/null
+++ b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.out
@@ -0,0 +1,14 @@
+# tar
+# tar
+# tar
+# cabal v2-update
+Downloading the latest package list from test-local-repo
+# cabal v2-build
+Resolving dependencies...
+Error: [Cabal-7107]
+Could not resolve dependencies:
+[__0] trying: a-0 (user goal)
+[__1] next goal: some-lib (dependency of a)
+[__1] fail (not a user-provided goal nor mentioned as a constraint when reject-unconstrained-dependencies=all)
+[__1] fail (backjumping, conflict set: a, some-lib)
+After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: a (2), some-lib (1)
diff --git a/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.project b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.project
new file mode 100644
index 00000000000..167c82a6219
--- /dev/null
+++ b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.project
@@ -0,0 +1,3 @@
+packages: .
+constraints: some-lib +some-flag
+reject-unconstrained-dependencies: all
diff --git a/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.test.hs b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.test.hs
new file mode 100644
index 00000000000..044f5d36759
--- /dev/null
+++ b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/cabal.test.hs
@@ -0,0 +1,24 @@
+import Test.Cabal.Prelude
+main = do
+  cabalTest . recordMode RecordMarked $ withRepo "repo" $ do
+    res <- fails $ cabal' "v2-build" ["all", "--dry-run"]
+    assertOutputContains "not a user-provided goal" res
+
+  -- The following all check version ranges that don't have a version
+  -- constrained dependency one way or another.
+
+  cabalTest' "any-flag" . recordMode RecordMarked $ withRepo "repo" $ do
+    res <- fails $ cabal' "v2-build" ["all", "--dry-run", "--constraint", "some-lib -any"]
+    assertOutputContains "not a user-provided goal" res
+
+  cabalTest' "any-version" . recordMode RecordMarked $ withRepo "repo" $ do
+    res <- fails $ cabal' "v2-build" ["all", "--dry-run", "--constraint", "some-lib >=0"]
+    assertOutputContains "not a user-provided goal" res
+
+  cabalTest' "none-flag" . recordMode RecordMarked $ withRepo "repo" $ do
+    res <- fails $ cabal' "v2-build" ["all", "--dry-run", "--constraint", "some-lib -none"]
+    assertOutputContains "not a user-provided goal" res
+
+  cabalTest' "none-version" . recordMode RecordMarked $ withRepo "repo" $ do
+    res <- fails $ cabal' "v2-build" ["all", "--dry-run", "--constraint", "some-lib <0"]
+    assertOutputContains "not a user-provided goal" res
diff --git a/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/repo b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/repo
new file mode 120000
index 00000000000..2dd2305a132
--- /dev/null
+++ b/cabal-testsuite/PackageTests/RequireExplicit/FlagNotVersion/repo
@@ -0,0 +1 @@
+../repo/
\ No newline at end of file
diff --git a/cabal-testsuite/PackageTests/RequireExplicit/MultiPkg/cabal.test.hs b/cabal-testsuite/PackageTests/RequireExplicit/MultiPkg/cabal.test.hs
index 271bddebf0b..11dd7c8e341 100644
--- a/cabal-testsuite/PackageTests/RequireExplicit/MultiPkg/cabal.test.hs
+++ b/cabal-testsuite/PackageTests/RequireExplicit/MultiPkg/cabal.test.hs
@@ -9,8 +9,18 @@ main = cabalTest . recordMode DoNotRecord $ withRepo "repo" $ do
   res <- fails $ cabal' "v2-build" ["all", "--dry-run", "--reject-unconstrained-dependencies", "all", "--constraint", "other-lib -any"]
   assertOutputContains "not a user-provided goal" res
 
-  -- everything's listed, good to go
-  cabal "v2-build" ["all", "--dry-run", "--reject-unconstrained-dependencies", "all", "--constraint", "other-lib -any", "--constraint", "some-exe -any"]
+  -- everything's listed, but -any is not a version constraint accepted by reject-unconstrained-dependencies=all
+  res <- fails $ cabal' "v2-build" ["all", "--dry-run", "--reject-unconstrained-dependencies", "all", "--constraint", "other-lib -any", "--constraint", "some-exe -any"]
+  assertOutputContains "not a user-provided goal" res
+
+  -- everything's listed, good to go if we give proper version constraints
+  res <- cabal' "v2-build" ["all", "--dry-run", "--reject-unconstrained-dependencies", "all", "--constraint", "some-lib ==1.0", "--constraint", "other-lib ==1.0", "--constraint", "some-exe ==1.0"]
+  assertOutputDoesNotContain "not a user-provided goal" res
+
+  -- a depends on b, but b is a local dependency, so it gets a pass, but we still need to provide version constraints for the other dependencies
+  res <- fails $ cabal' "v2-build" ["a", "--dry-run", "--reject-unconstrained-dependencies", "all", "--constraint", "other-lib -any", "--constraint", "some-exe -any"]
+  assertOutputContains "not a user-provided goal" res
 
-  -- a depends on b, but b is a local dependency, so it gets a pass
-  cabal "v2-build" ["a", "--dry-run", "--reject-unconstrained-dependencies", "all", "--constraint", "other-lib -any", "--constraint", "some-exe -any"]
+  -- a depends on b, but b is a local dependency, so it gets a pass and we're good to go if we give proper version constraints
+  res <- cabal' "v2-build" ["a", "--dry-run", "--reject-unconstrained-dependencies", "all", "--constraint", "some-lib ==1.0", "--constraint", "other-lib ==1.0", "--constraint", "some-exe ==1.0"]
+  assertOutputDoesNotContain "not a user-provided goal" res
diff --git a/changelog.d/12191.md b/changelog.d/12191.md
new file mode 100644
index 00000000000..c5b2555b20a
--- /dev/null
+++ b/changelog.d/12191.md
@@ -0,0 +1,11 @@
+---
+synopsis: Reject dependencies with unconstrained versions
+packages: [cabal-install]
+prs: 12191
+issues: 12190
+---
+
+Change the behaviour of `--reject-unconstrained-dependencies=all` so that it is
+not satisfied by flag constraints. Only version constraints should satisfy this
+check and even then these need to reject at least some versions so `>=0` or
+`-any` and `<0` or `-none` as version constraint will also fail the check.