--- a/configure.ac
+++ b/configure.ac
@@ -2530,7 +2530,7 @@ AC_ARG_WITH([ssl-engine],
 )
 
 if test "x$openssl" = "xyes" ; then
-	LIBS="-lcrypto $LIBS"
+	LIBS="-lcrypto -lpthread $LIBS"
 	AC_TRY_LINK_FUNC([RAND_add], ,
 	    [AC_MSG_ERROR([*** working libcrypto not found, check config.log])])
 	AC_CHECK_HEADER([openssl/opensslv.h], ,