diff --git a/test/test_protocol.cxx b/test/test_protocol.cxx
index e80e4fe6d..fb35cbc66 100644
--- a/test/test_protocol.cxx
+++ b/test/test_protocol.cxx
@@ -8,7 +8,7 @@
 #include <cppunit/ui/text/TestRunner.h>
 #include <cppunit/extensions/HelperMacros.h>
 
-#include <unistd.h>
+#include <stdlib.h>
 
 static enum ack last_error = ack(-1);