diff --git a/c-programming/io/pure_getline.c b/c-programming/io/pure_getline.c
index a7e750c..6017263 100644
--- a/c-programming/io/pure_getline.c
+++ b/c-programming/io/pure_getline.c
@@ -17,6 +17,11 @@ bool pure_getline(char** output) {
 	 * 	false: an error occurred, see errno
 	 */
 
+	if (output == NULL) {
+		errno = EINVAL;
+		return false;
+	}
+
 	char* line = NULL;
 	size_t len = 0;
 	int character;