diff --git a/Python/ceval.c b/Python/ceval.c
index d1d6d1d..e693147 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1446,7 +1446,10 @@
 		TARGET(BINARY_MODULO)
 			w = POP();
 			v = TOP();
-			x = PyNumber_Remainder(v, w);
+			if (PyUnicode_CheckExact(v))
+				x = PyUnicode_Format(v, w);
+			else
+				x = PyNumber_Remainder(v, w);
 			Py_DECREF(v);
 			Py_DECREF(w);
 			SET_TOP(x);