diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
index 578a173d4873..9228f60e2a20 100644
--- a/tools/perf/util/expr.c
+++ b/tools/perf/util/expr.c
@@ -32,6 +32,26 @@ static bool key_equal(const void *key1, const void *key2,
 	return !strcmp((const char *)key1, (const char *)key2);
 }
 
+/* Caller must make sure id is allocated */
+int expr__add_id(struct expr_parse_ctx *ctx, const char *id)
+{
+	struct expr_id_data *data_ptr = NULL, *old_data = NULL;
+	char *old_key = NULL;
+	int ret;
+
+	data_ptr = malloc(sizeof(*data_ptr));
+	if (!data_ptr)
+		return -ENOMEM;
+
+	ret = hashmap__set(&ctx->ids, id, data_ptr,
+			   (const void **)&old_key, (void **)&old_data);
+	if (ret)
+		free(data_ptr);
+	free(old_key);
+	free(old_data);
+	return ret;
+}
+
 /* Caller must make sure id is allocated */
 int expr__add_id_val(struct expr_parse_ctx *ctx, const char *id, double val)
 {
@@ -39,12 +59,11 @@ int expr__add_id_val(struct expr_parse_ctx *ctx, const char *id, double val)
 	char *old_key = NULL;
 	int ret;
 
-	if (val != 0.0) {
-		data_ptr = malloc(sizeof(*data_ptr));
-		if (!data_ptr)
-			return -ENOMEM;
-		data_ptr->val = val;
-	}
+	data_ptr = malloc(sizeof(*data_ptr));
+	if (!data_ptr)
+		return -ENOMEM;
+	data_ptr->val = val;
+
 	ret = hashmap__set(&ctx->ids, id, data_ptr,
 			   (const void **)&old_key, (void **)&old_data);
 	if (ret)
diff --git a/tools/perf/util/expr.h b/tools/perf/util/expr.h
index 21fe5bd85718..ac32cda42006 100644
--- a/tools/perf/util/expr.h
+++ b/tools/perf/util/expr.h
@@ -26,6 +26,7 @@ struct expr_scanner_ctx {
 
 void expr__ctx_init(struct expr_parse_ctx *ctx);
 void expr__ctx_clear(struct expr_parse_ctx *ctx);
+int expr__add_id(struct expr_parse_ctx *ctx, const char *id);
 int expr__add_id_val(struct expr_parse_ctx *ctx, const char *id, double val);
 int expr__get_id(struct expr_parse_ctx *ctx, const char *id, double *val_ptr);
 int expr__parse(double *final_val, struct expr_parse_ctx *ctx,
diff --git a/tools/perf/util/expr.y b/tools/perf/util/expr.y
index b2b3420ea6ec..8befe4a46f87 100644
--- a/tools/perf/util/expr.y
+++ b/tools/perf/util/expr.y
@@ -69,7 +69,7 @@ all_other: all_other other
 
 other: ID
 {
-	expr__add_id_val(ctx, $1, 0.0);
+	expr__add_id(ctx, $1);
 }
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