diff --git a/nse_ssl_cert.cc b/nse_ssl_cert.cc
index 94bc941bd..818b657ed 100644
--- a/nse_ssl_cert.cc
+++ b/nse_ssl_cert.cc
@@ -92,6 +92,7 @@
 #include <assert.h>
 #include <ctype.h>
 #include <errno.h>
+#include <string.h>
 #include <openssl/bio.h>
 #include <openssl/pem.h>
 #include <openssl/ssl.h>