diff --git a/java/ql/lib/semmle/code/java/security/PathSanitizer.qll b/java/ql/lib/semmle/code/java/security/PathSanitizer.qll
index 4685f5e48f7..ffd50655001 100644
--- a/java/ql/lib/semmle/code/java/security/PathSanitizer.qll
+++ b/java/ql/lib/semmle/code/java/security/PathSanitizer.qll
@@ -427,20 +427,17 @@ private class ReplaceDirectoryCharactersSanitizer extends StringReplaceOrReplace
   }
 }
 
-/** Holds if `target` is the first argument of `matchesCall`. */
-private predicate isMatchesTarget(StringMatchesCall matchesCall, CompileTimeConstantExpr target) {
-  target = matchesCall.getArgument(0)
-}
-
 /**
  * Holds if `matchesCall` confirms that `checkedExpr` does not contain any directory characters
  * on the given `branch`.
  */
-private predicate isMatchesCall(StringMatchesCall matchesCall, Expr checkedExpr, boolean branch) {
+private predicate isMatchesCall(
+  RegexExecutionExpr::Range regexMatch, Expr checkedExpr, boolean branch
+) {
   exists(CompileTimeConstantExpr target, string targetValue |
-    isMatchesTarget(matchesCall, target) and
+    target = regexMatch.getRegex() and
     target.getStringValue() = targetValue and
-    checkedExpr = matchesCall.getQualifier()
+    checkedExpr = regexMatch.getString()
   |
     (
       // Allow anything except `.`, '/', '\'
diff --git a/java/ql/lib/semmle/code/java/security/Sanitizers.qll b/java/ql/lib/semmle/code/java/security/Sanitizers.qll
index 3f909864d2c..ddac010391e 100644
--- a/java/ql/lib/semmle/code/java/security/Sanitizers.qll
+++ b/java/ql/lib/semmle/code/java/security/Sanitizers.qll
@@ -46,19 +46,11 @@ predicate regexpMatchGuardChecks(Guard guard, Expr e, boolean branch) {
     guard = mc and
     branch = true
   |
-    // `String.matches` and other `matches` methods.
+    e = mc.(RegexExecutionExpr::Range).getString()
+    or
+    // Other `matches` methods.
     method.getName() = "matches" and
     e = mc.getQualifier()
-    or
-    method instanceof PatternMatchesMethod and
-    e = mc.getArgument(1)
-    or
-    method instanceof MatcherMatchesMethod and
-    exists(MethodCall matcherCall |
-      matcherCall.getMethod() instanceof PatternMatcherMethod and
-      e = matcherCall.getArgument(0) and
-      DataFlow::localExprFlow(matcherCall, mc.getQualifier())
-    )
   )
 }