diff --git a/tools/build/gen-cat.nqp b/tools/build/gen-cat.nqp
index c981b2f56f0..dcce33e10c6 100755
--- a/tools/build/gen-cat.nqp
+++ b/tools/build/gen-cat.nqp
@@ -43,7 +43,7 @@ sub MAIN(*@ARGS) {
             } elsif $in_omit {
                 print("\n");
             } else {
-                if $_ ~~ /'#?js: NFG'/ {
+                if $backend eq 'js' && $_ ~~ /'#?js: NFG'/ {
                     print(subst($_, /nqp\:\:[chars|substr|iseq_s|iscclass]/,
                         -> $op {$op ~ 'nfg'}, :global));
                 } else {