diff --git a/CMakeLists.txt b/CMakeLists.txt
index 00c37dd..3e14c82 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -72,6 +72,8 @@
     if("${SWIG_VERSION}" VERSION_GREATER "1.3.30")
         set(SWIG_VERSION_CHECK TRUE)
     endif()
+else()
+    message(FATAL_ERROR "SWIG required to compile gr-gsm")
 endif(SWIG_FOUND)