diff --git a/Sources/_MatchingEngine/Regex/Parse/LexicalAnalysis.swift b/Sources/_MatchingEngine/Regex/Parse/LexicalAnalysis.swift
index e917b6a8a..99e97727e 100644
--- a/Sources/_MatchingEngine/Regex/Parse/LexicalAnalysis.swift
+++ b/Sources/_MatchingEngine/Regex/Parse/LexicalAnalysis.swift
@@ -1136,7 +1136,7 @@ extension Source {
       }
 
       // References that look like groups, e.g (?R), (?1), ...
-      if let ref = try src.lexGroupLikeReference() {
+      if !customCC, let ref = try src.lexGroupLikeReference() {
         return ref.value
       }
 
diff --git a/Tests/RegexTests/ParseTests.swift b/Tests/RegexTests/ParseTests.swift
index ddb8dcbad..6dd38d28d 100644
--- a/Tests/RegexTests/ParseTests.swift
+++ b/Tests/RegexTests/ParseTests.swift
@@ -831,6 +831,10 @@ extension RegexTests {
     parseTest(#"(?P>+1)"#, subpattern(.named("+1")))
     parseTest(#"(?P=+1)"#, backreference(.named("+1")))
 
+    parseTest(#"[(?R)]"#, charClass("(", "?", "R", ")"))
+    parseTest(#"[(?&a)]"#, charClass("(", "?", "&", "a", ")"))
+    parseTest(#"[(?1)]"#, charClass("(", "?", "1", ")"))
+
     parseTest(#"\g<1>"#, subpattern(.absolute(1)))
     parseTest(#"\g<001>"#, subpattern(.absolute(1)))
     parseTest(#"\g'52'"#, subpattern(.absolute(52)))