diff --git a/src/extstring.c b/src/extstring.c
index 3886a60..ba7adcb 100644
--- a/src/extstring.c
+++ b/src/extstring.c
@@ -10,6 +10,7 @@ void es_addsymbol(tExtstring* string, char symbol) {
 	};
 	ptr->next = malloc(sizeof(tExtstring));
 	ptr->next->symbol = symbol;
+	ptr->next->next = NULL;
 	return;
 }