diff --git a/README.md b/README.md
index 443dc7c3..bb672c61 100644
--- a/README.md
+++ b/README.md
@@ -458,6 +458,8 @@ def app(environ, start_response):
     return iter([data])
 ```
 
+**Note: don't initialize metric with MultiProcessCollector registry argument.**
+
 **Three**: Instrumentation
 
 Counters, Summarys and Histograms work as normal.