diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1ea35e7030..990c745b5f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -419,6 +419,7 @@ count_true(enabled_ssl_options_count
   CURL_USE_MBEDTLS
   CURL_USE_BEARSSL
   CURL_USE_WOLFSSL
+  CURL_USE_GNUTLS
 )
 if(enabled_ssl_options_count GREATER "1")
   set(CURL_WITH_MULTI_SSL ON)