diff --git a/compat/winansi.c b/compat/winansi.c
index 3ce1900939..601f5c0144 100644
--- a/compat/winansi.c
+++ b/compat/winansi.c
@@ -546,6 +546,9 @@ static void detect_msys_tty(int fd)
 	if (!NT_SUCCESS(NtQueryObject(h, ObjectNameInformation,
 			buffer, sizeof(buffer) - 2, &result)))
 		return;
+	if (result < sizeof(*nameinfo) || !nameinfo->Name.Buffer ||
+		!nameinfo->Name.Length)
+		return;
 	name = nameinfo->Name.Buffer;
 	name[nameinfo->Name.Length / sizeof(*name)] = 0;