diff --git a/unit_test/scale_argb_test.cc b/unit_test/scale_argb_test.cc
index b383c8515..5991ee8c8 100644
--- a/unit_test/scale_argb_test.cc
+++ b/unit_test/scale_argb_test.cc
@@ -226,6 +226,7 @@ TEST_FACTOR(4, 1 / 4, 1 / 4)
 TEST_FACTOR(8, 1 / 8, 1 / 8)
 TEST_FACTOR(3by4, 3 / 4, 3 / 4)
 TEST_FACTOR(3by8, 3 / 8, 3 / 8)
+TEST_FACTOR(3, 1 / 3, 1 / 3)
 #undef TEST_FACTOR1
 #undef TEST_FACTOR
 
diff --git a/unit_test/scale_test.cc b/unit_test/scale_test.cc
index d1e681c5f..5d9ca98f4 100644
--- a/unit_test/scale_test.cc
+++ b/unit_test/scale_test.cc
@@ -290,6 +290,7 @@ TEST_FACTOR(4, 1 / 4, 1 / 4)
 TEST_FACTOR(8, 1 / 8, 1 / 8)
 TEST_FACTOR(3by4, 3 / 4, 3 / 4)
 TEST_FACTOR(3by8, 3 / 8, 3 / 8)
+TEST_FACTOR(3, 1 / 3, 1 / 3)
 #undef TEST_FACTOR1
 #undef TEST_FACTOR