diff --git a/rtc_base/opensslutility.cc b/rtc_base/opensslutility.cc
index 2b4ffb6960..bf6832c5e6 100644
--- a/rtc_base/opensslutility.cc
+++ b/rtc_base/opensslutility.cc
@@ -23,6 +23,7 @@
 
 #include <openssl/bio.h>
 #include <openssl/crypto.h>
+#include <openssl/err.h>
 #include <openssl/x509.h>
 #include <openssl/x509v3.h>