diff --git a/javascript/ql/lib/semmle/javascript/security/performance/ReDoSUtil.qll b/javascript/ql/lib/semmle/javascript/security/performance/ReDoSUtil.qll
index 3bdd47470fb..43601b1d407 100644
--- a/javascript/ql/lib/semmle/javascript/security/performance/ReDoSUtil.qll
+++ b/javascript/ql/lib/semmle/javascript/security/performance/ReDoSUtil.qll
@@ -422,12 +422,7 @@ private module CharacterClasses {
     char = "0123456789".charAt(_)
     or
     clazz = "s" and
-    (
-      char = [" ", "\t", "\r", "\n"]
-      or
-      char = getARelevantChar() and
-      char.regexpMatch("\\u000b|\\u000c") // \v|\f (vertical tab | form feed)
-    )
+    char = [" ", "\t", "\r", "\n", 11.toUnicode(), 12.toUnicode()] // 11.toUnicode() = \v, 12.toUnicode() = \f
     or
     clazz = "w" and
     char = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_".charAt(_)
diff --git a/python/ql/lib/semmle/python/security/performance/ReDoSUtil.qll b/python/ql/lib/semmle/python/security/performance/ReDoSUtil.qll
index 3bdd47470fb..43601b1d407 100644
--- a/python/ql/lib/semmle/python/security/performance/ReDoSUtil.qll
+++ b/python/ql/lib/semmle/python/security/performance/ReDoSUtil.qll
@@ -422,12 +422,7 @@ private module CharacterClasses {
     char = "0123456789".charAt(_)
     or
     clazz = "s" and
-    (
-      char = [" ", "\t", "\r", "\n"]
-      or
-      char = getARelevantChar() and
-      char.regexpMatch("\\u000b|\\u000c") // \v|\f (vertical tab | form feed)
-    )
+    char = [" ", "\t", "\r", "\n", 11.toUnicode(), 12.toUnicode()] // 11.toUnicode() = \v, 12.toUnicode() = \f
     or
     clazz = "w" and
     char = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_".charAt(_)