diff --git a/fipstools/cavp_tlskdf_test.cc b/fipstools/cavp_tlskdf_test.cc
index ac0f83f..0af2d47 100644
--- a/fipstools/cavp_tlskdf_test.cc
+++ b/fipstools/cavp_tlskdf_test.cc
@@ -18,6 +18,8 @@
 
 #include <vector>
 
+#include <errno.h>
+
 #include <openssl/digest.h>
 
 #include "cavp_test_util.h"