diff --git a/src/rules/customrules.jl b/src/rules/customrules.jl
index 0a8b950a63..111875d636 100644
--- a/src/rules/customrules.jl
+++ b/src/rules/customrules.jl
@@ -1101,7 +1101,7 @@ end
     end
 
     if !forward
-	funcTy = rev_TT.parameters[isKWCall ? 5 : 2 + (!applicablefn)]
+	funcTy = rev_TT.parameters[(isKWCall ? 5 : 2) + (!applicablefn)]
         if needsTape
             @assert tape != C_NULL
             tape_idx =