diff --git a/Lib/multiprocessing/managers.py b/Lib/multiprocessing/managers.py
index f32dab19afe..e331116c89d 100644
--- a/Lib/multiprocessing/managers.py
+++ b/Lib/multiprocessing/managers.py
@@ -410,7 +410,7 @@ class Server(object):
             self.id_to_refcount[ident] -= 1
             if self.id_to_refcount[ident] == 0:
                 del self.id_to_obj[ident], self.id_to_refcount[ident]
-                util.debug('disposing of obj with id %d', ident)
+                util.debug('disposing of obj with id %r', ident)
         finally:
             self.mutex.release()
 
diff --git a/Misc/NEWS b/Misc/NEWS
index 3326bd94b07..c3c105b3175 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -82,6 +82,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #6938: Fix a TypeError in string formatting of a multiprocessing
+  debug message.
+
 - Issue #6635: Fix profiler printing usage message.
 
 - Issue #6795: int(Decimal('nan')) now raises ValueError instead of