diff --git a/jpegut.c b/jpegut.c
index 995d5442..6861e67a 100644
--- a/jpegut.c
+++ b/jpegut.c
@@ -638,8 +638,10 @@ int main(int argc, char *argv[])
 		dotest(39, 41, 3, TJ_422, "test");
 		dotest(48, 48, 3, TJ_420, "test");
 		dotest(41, 35, 3, TJ_420, "test");
+		dotest(48, 48, 3, TJ_GRAYSCALE, "test");
+		dotest(35, 39, 3, TJ_GRAYSCALE, "test");
 		dotest(48, 48, 1, TJ_GRAYSCALE, "test");
-		dotest(35, 39, 1, TJ_GRAYSCALE, "test");
+		dotest(39, 41, 1, TJ_GRAYSCALE, "test");
 	}
 
 	return exitstatus;