diff --git a/test/test_error.c b/test/test_error.c
index 55f56d3..a0c6165 100644
--- a/test/test_error.c
+++ b/test/test_error.c
@@ -14,9 +14,11 @@ This file is part of H5Z-ZFP. Please also read the BSD license
 #include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
 #include <unistd.h>
 
+#define _GNU_SOURCE
+#include <string.h>
+
 #include "hdf5.h"
 
 #ifdef H5Z_ZFP_USE_PLUGIN