diff --git a/src/proto.cc b/src/proto.cc
index bef65bd..1807080 100644
--- a/src/proto.cc
+++ b/src/proto.cc
@@ -200,7 +200,7 @@ int _proto_list_str(int pid, char* proto_path)
         return -1;
     }
 
-    if (str == NULL) {
+    if (proto_path == NULL) {
         return -1;
     }