diff --git a/crypto/cversion.c b/crypto/cversion.c
index aa479a9409290b730c1618c57199514152442453..8e41fcef7467edd27ae0e98a5ce0d5922efc05d5 100644
--- a/crypto/cversion.c
+++ b/crypto/cversion.c
@@ -62,7 +62,7 @@
 # include "buildinf.h"
 #endif
 
-unsigned long OpenSSL_version_num()
+unsigned long OpenSSL_version_num(void)
 {
     return OPENSSL_VERSION_NUMBER;
 }