diff --git a/diff.c b/diff.c
index 17a2b4df29..8d8405aba2 100644
--- a/diff.c
+++ b/diff.c
@@ -2799,6 +2799,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		;
 	else if (!prefixcmp(arg, "--output=")) {
 		options->file = fopen(arg + strlen("--output="), "w");
+		if (!options->file)
+			die_errno("Could not open '%s'", arg + strlen("--output="));
 		options->close_file = 1;
 	} else
 		return 0;