diff --git a/common/rfb/SSecurityVeNCrypt.cxx b/common/rfb/SSecurityVeNCrypt.cxx
index 926edaa..860e440 100644
--- a/common/rfb/SSecurityVeNCrypt.cxx
+++ b/common/rfb/SSecurityVeNCrypt.cxx
@@ -26,6 +26,10 @@
 #include <config.h>
 #endif
 
+#ifndef HAVE_GNUTLS
+#error "This source should not be compiled without HAVE_GNUTLS defined"
+#endif
+
 #include <rfb/SSecurityVeNCrypt.h>
 #include <rfb/Exception.h>
 #include <rfb/LogWriter.h>