1 files changed, 1 insertions, 0 deletions
diff --git a/parse.y b/parse.y
index 7eaab6b1b8..7bf3149e2b 100644
--- a/parse.y
+++ b/parse.y
@@ -3810,6 +3810,7 @@ string		: tCHAR
 		| string string1
 		    {
 		    /*%%%*/
+			rb_warning0("string concatenation syntax will be deprecated");
 			$$ = literal_concat($1, $2);
 		    /*%
 			$$ = dispatch2(string_concat, $1, $2);