diff --git a/test/v3ext.c b/test/v3ext.c
index 7a240cd706..6cec6f1a9b 100644
--- a/test/v3ext.c
+++ b/test/v3ext.c
@@ -15,6 +15,7 @@
 #include <openssl/err.h>
 #include "internal/nelem.h"
 
+#include <string.h>
 #include "testutil.h"
 
 static const char *infile;

Fix compilation error when building OpenSSL 1.1.1q in MacOS 11+
Fix compilation error when building OpenSSL 1.1.1q in MacOS 11+

"error: implicitly declaring library function 'memcmp'"
Downstream backport of https://github.com/openssl/openssl/issues/18720
