diff --git a/src/ascii_cmd.c b/src/ascii_cmd.c
index 90d9a83..050c105 100644
--- a/src/ascii_cmd.c
+++ b/src/ascii_cmd.c
@@ -426,8 +426,9 @@ static bool process_command_table(const command_handler_t *table, int table_size
 }
 
 void process_ascii_cmd(RDSModulator* mod, char *str) {
-    char *cmd, *arg, *output;
-    memset(output, 0, 255);
+    char *cmd, *arg;
+    char output[255];
+    memset(output, 0, sizeof(output));
     
     uint16_t cmd_len = _strnlen((const char*)str, CTL_BUFFER_SIZE);