diff --git a/diff.c b/diff.c
index d156ff252fda8830f75401a6b31f87c03250f775..db5e84443bfe915b5e44ec2fc573ebdb95dd20c1 100644
--- a/diff.c
+++ b/diff.c
@@ -2391,10 +2391,14 @@ int diff_populate_filespec(struct diff_filespec *s, int size_only)
 	}
 	else {
 		enum object_type type;
-		if (size_only)
+		if (size_only) {
 			type = sha1_object_info(s->sha1, &s->size);
-		else {
+			if (type < 0)
+				die("unable to read %s", sha1_to_hex(s->sha1));
+		} else {
 			s->data = read_sha1_file(s->sha1, &type, &s->size);
+			if (!s->data)
+				die("unable to read %s", sha1_to_hex(s->sha1));
 			s->should_free = 1;
 		}
 	}