diff --git a/Lib/test/test_opcodes.py b/Lib/test/test_opcodes.py
index d7d1673..7985bf6 100644
--- a/Lib/test/test_opcodes.py
+++ b/Lib/test/test_opcodes.py
@@ -102,6 +102,12 @@
         g = eval('lambda a=1: None')
         self.assertNotEquals(f, g)
 
+    def test_modulo_of_string_subclasses(self):
+        class MyString(str):
+            def __mod__(self, value):
+                return 42
+        self.assertEqual(MyString() % 3, 42)
+
 
 def test_main():
     run_unittest(OpcodeTest)
diff --git a/Python/ceval.c b/Python/ceval.c
index d457fd5..419ecfa 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1283,7 +1283,10 @@
 		case BINARY_MODULO:
 			w = POP();
 			v = TOP();
-			x = PyNumber_Remainder(v, w);
+			if (PyString_CheckExact(v))
+				x = PyString_Format(v, w);
+			else
+				x = PyNumber_Remainder(v, w);
 			Py_DECREF(v);
 			Py_DECREF(w);
 			SET_TOP(x);