diff --git a/lib/vers/parser.rb b/lib/vers/parser.rb
index dc68d32..ceef528 100644
--- a/lib/vers/parser.rb
+++ b/lib/vers/parser.rb
@@ -66,7 +66,7 @@ def parse(vers_string, require_canonical_order: false)
       unless vers_string.is_a?(String) && vers_string.start_with?("vers:")
         raise ArgumentError, "Invalid vers URI format: #{vers_string}"
       end
-      if vers_string.match?(/[ \t\r\n]/)
+      if vers_string.match?(/[\t\r\n]/) || (require_canonical_order && vers_string.include?(" "))
         raise ArgumentError, "non-canonical VERS: whitespace is not permitted"
       end
 
@@ -82,9 +82,13 @@ def parse(vers_string, require_canonical_order: false)
       end
       scheme = Scheme.canonical(raw_scheme)
       constraints_string = remainder[(slash + 1)..]
-      if constraints_string.empty? || constraints_string == "*"
+      if constraints_string.empty?
+        if require_canonical_order
+          raise ArgumentError, "non-canonical VERS: constraints must not be empty"
+        end
         return VersionRange.unbounded(scheme: scheme)
       end
+      return VersionRange.unbounded(scheme: scheme) if constraints_string == "*"
 
       validate_vers_constraints!(constraints_string, scheme, require_canonical_order)
 
@@ -279,6 +283,9 @@ def validate_vers_version!(version, scheme)
         if lowercase_ascii_hex?(first) || lowercase_ascii_hex?(second)
           raise ArgumentError, "non-canonical VERS: percent-encoding in version is not canonical"
         end
+        if first == 48 && [57, 65, 66, 67, 68].include?(second)
+          raise ArgumentError, "non-canonical VERS: whitespace is not permitted"
+        end
 
         index += 3
       end
diff --git a/lib/vers/special_version.rb b/lib/vers/special_version.rb
index d46043c..9e45307 100644
--- a/lib/vers/special_version.rb
+++ b/lib/vers/special_version.rb
@@ -289,8 +289,8 @@ module IntDotVersion
     extend self
 
     def compare(left, right)
-      left_parts = left.to_s.split(".", -1)
-      right_parts = right.to_s.split(".", -1)
+      left_parts = left.to_s[/\A[\d.]*/].split(".", -1)
+      right_parts = right.to_s[/\A[\d.]*/].split(".", -1)
 
       [left_parts.length, right_parts.length].max.times do |index|
         comparison = VersionComparison.compare_numbers(left_parts[index], right_parts[index])
diff --git a/test/test_range_conformance.rb b/test/test_range_conformance.rb
index f3fef39..f580197 100644
--- a/test/test_range_conformance.rb
+++ b/test/test_range_conformance.rb
@@ -44,8 +44,8 @@ class TestRangeConformance < Minitest::Test
             when "parse"
               range = Vers::Parser.new.parse(test_case.fetch("input"), require_canonical_order: true)
               {
-                "scheme" => range.scheme,
-                "version_constraints" => range_constraints(range)
+                "type" => range.scheme,
+                "constraints" => range_constraints(range)
               }
             when "validate"
               range = Vers.parse(test_case.fetch("input"))
diff --git a/test/vers-spec b/test/vers-spec
index 93ff155..ec1a0c8 160000
--- a/test/vers-spec
+++ b/test/vers-spec
@@ -1 +1 @@
-Subproject commit 93ff155247ea34986e76476556ba46c31f3bed69
+Subproject commit ec1a0c8143b105a054b0f7cb1feb368b85c9c781