diff --git a/src/pygit2/config.c b/src/pygit2/config.c
index cd21342..0cbee92 100644
--- a/src/pygit2/config.c
+++ b/src/pygit2/config.c
@@ -235,7 +235,7 @@ Config_foreach_callback_wrapper(const git_config_entry *entry, void *c_payload)
     if (!(py_result = PyObject_CallObject(py_callback,args)))
         return -1;
 
-    if (!(c_result = PyLong_AsLong(py_result)))
+    if (c_result = PyLong_AsLong(py_result) == -1)
         return -1;
 
     return c_result;