diff --git a/test/read_mixer.cxx b/test/read_mixer.cxx
index de77a00c4..83a1d26b4 100644
--- a/test/read_mixer.cxx
+++ b/test/read_mixer.cxx
@@ -35,6 +35,7 @@
 #include <assert.h>
 #include <string.h>
 #include <unistd.h>
+#include <stdlib.h>
 
 const struct filter_plugin *
 filter_plugin_by_name(gcc_unused const char *name)