diff -r c1a698edfa1b Modules/_functoolsmodule.c
--- a/Modules/_functoolsmodule.c	Tue Aug 23 16:22:35 2016 +0200
+++ b/Modules/_functoolsmodule.c	Tue Aug 23 16:32:57 2016 +0200
@@ -160,19 +160,23 @@ partial_call(partialobject *pto, PyObjec
         Py_XINCREF(kwappl);
     }
     else {
-        kwappl = PyDict_Copy(pto->kw);
-        if (kwappl == NULL) {
-            Py_XDECREF(argappl);
-            return NULL;
-        }
+        if (kw != NULL) {
+            kwappl = PyDict_Copy(pto->kw);
+            if (kwappl == NULL) {
+                Py_XDECREF(argappl);
+                return NULL;
+            }
 
-        if (kw != NULL) {
             if (PyDict_Merge(kwappl, kw, 1) != 0) {
                 Py_XDECREF(argappl);
                 Py_DECREF(kwappl);
                 return NULL;
             }
         }
+        else {
+            kwappl = pto->kw;
+            Py_INCREF(kwappl);
+        }
     }
 
     if (stack) {