diff --git a/src/alloc.c b/src/alloc.c
index 41b2f9e77d2..8dae6bffbd9 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -6907,7 +6907,8 @@ sweep_misc (void)
 	      else if (mblk->markers[i].m.u_any.type == Lisp_Misc_User_Ptr)
 		{
 		  struct Lisp_User_Ptr *uptr = &mblk->markers[i].m.u_user_ptr;
-		  uptr->finalizer (uptr->p);
+		  if (uptr->finalizer)
+		    uptr->finalizer (uptr->p);
 		}
 #endif
               /* Set the type of the freed object to Lisp_Misc_Free.