diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
index 21e82a1e11a2..3b49b230b111 100644
--- a/tools/perf/util/expr.y
+++ b/tools/perf/util/expr.y
@@ -27,6 +27,7 @@
 %token EXPR_PARSE EXPR_OTHER EXPR_ERROR
 %token <num> NUMBER
 %token <str> ID
+%destructor { free ($$); } <str>
 %token MIN MAX IF ELSE SMT_ON
 %left MIN MAX IF
 %left '|'
@@ -94,8 +95,10 @@ if_expr:
 expr:	  NUMBER
 	| ID			{ if (lookup_id(ctx, $1, &$$) < 0) {
 					pr_debug("%s not found\n", $1);
+					free($1);
 					YYABORT;
 				  }
+				  free($1);
 				}
 	| expr '|' expr		{ $$ = (long)$1 | (long)$3; }
 	| expr '&' expr		{ $$ = (long)$1 & (long)$3; }