diff --git a/apisix/plugins/brotli.lua b/apisix/plugins/brotli.lua
index f8522e98ae8a..e458ac57dc65 100644
--- a/apisix/plugins/brotli.lua
+++ b/apisix/plugins/brotli.lua
@@ -158,12 +158,15 @@ local function weak_etag_header()
         return
     end
 
-    local regex = [[^(W/)?"(.*)"$]]
+    local regex = [[^(W/)?"([^"]*)"$]]
     local matched, err = ngx.re.match(etag, regex, "jo")
-    if not matched or err then
-        -- not standard etag, no quote
+    if err then
+        core.log.error("failed to match etag: ", err)
+    end
+    if not matched then
+        -- non-standard etag (not quoted) or a match failure; it cannot be
+        -- weakened, so drop it
         core.response.set_header("Etag", nil)
-        core.log.error("no standard etag or regex match failed: ", err)
         return
     end
 
diff --git a/t/plugin/brotli.t b/t/plugin/brotli.t
index 7e83e1c7bad3..ae3e31254617 100644
--- a/t/plugin/brotli.t
+++ b/t/plugin/brotli.t
@@ -833,8 +833,8 @@ Content-Encoding: br
 Vary:
 Etag:
 Content-Length:
---- error_log
-no standard etag or regex match failed:
+--- no_error_log
+[error]
 
 
 
@@ -888,3 +888,22 @@ Vary:
 Etag: W/"123456789"
 Last-Modified: Thu, 27 Nov 2025 00:32:33 GMT
 Content-Length:
+
+
+
+=== TEST 37: etag with embedded quotes is non-standard, clear it
+--- request
+POST /echo
+0123456789
+012345678
+--- more_headers
+Accept-Encoding: br
+Content-Type: text/html
+Etag: "12"34"
+--- response_headers
+Content-Encoding: br
+Vary:
+Etag:
+Content-Length:
+--- no_error_log
+[error]