diff --git a/prometheus/process_collector_test.go b/prometheus/process_collector_test.go
index c7acb47..d59ad77 100644
--- a/prometheus/process_collector_test.go
+++ b/prometheus/process_collector_test.go
@@ -1,3 +1,5 @@
+// +build linux
+
 package prometheus
 
 import (