diff --git a/c-programming/io/freadln.c b/c-programming/io/freadln.c
index a98c5f4..9a56378 100644
--- a/c-programming/io/freadln.c
+++ b/c-programming/io/freadln.c
@@ -37,8 +37,10 @@ int freadln(FILE* f, char** output, size_t* length_out) {
 	freadln_length_type length = 0; // initial length
 
 	*output = malloc((length + 1) * sizeof(char));
-	if (*output == NULL)
+	if (*output == NULL) {
+		errno = EINVAL;
 		return freadln_ERROR;
+	}
 
 	int character;
 	while ((character = fgetc(f)) != EOF