diff --git a/tccpp.c b/tccpp.c
index 0d00cbca..d03adc0f 100644
--- a/tccpp.c
+++ b/tccpp.c
@@ -2771,6 +2771,7 @@ static void next(void)
             } else {
                 /* end of macro string: free it */
                 tok_str_free(macro_ptr_allocated);
+                macro_ptr_allocated = NULL;
                 macro_ptr = NULL;
             }
             goto redo;