diff --git a/tool/smarts/src/main/java/org/openscience/cdk/smirks/Smirks.java b/tool/smarts/src/main/java/org/openscience/cdk/smirks/Smirks.java
index 8a90aa2fb1..689cb5fd27 100644
--- a/tool/smarts/src/main/java/org/openscience/cdk/smirks/Smirks.java
+++ b/tool/smarts/src/main/java/org/openscience/cdk/smirks/Smirks.java
@@ -672,7 +672,7 @@ else if (begNborIdx != endNborIdx) {
 
     private static String generateAtom(IAtom atom) {
         return "[" + Smarts.generateAtom(((QueryAtom) atom).getExpression())
-                           .replaceAll("^\\[|]$", "") + ":" + getMapIdx(atom) + "]";
+                           .replaceAll("(?:^\\[)|(?:]$)", "") + ":" + getMapIdx(atom) + "]";
     }
 
     private static void checkAtomMap(SmirksState state, IAtom atom) {