diff --git a/cmake/Dependencies.cmake b/cmake/Dependencies.cmake
index c4661e3..0e0150d 100644
--- a/cmake/Dependencies.cmake
+++ b/cmake/Dependencies.cmake
@@ -873,7 +873,7 @@ if(BUILD_PYTHON)
   if(Python_Development.Module_FOUND)
     if(USE_NUMPY)
       if(NOT Python_NumPy_FOUND)
-        message(WARNING "NumPy could not be found. Not building with NumPy. Suppress this warning with -DUSE_NUMPY=OFF")
+        message(FATAL_ERROR "NumPy could not be found. Not building with NumPy. Suppress this warning with -DUSE_NUMPY=OFF")
         caffe2_update_option(USE_NUMPY OFF)
       else()
         caffe2_update_option(USE_NUMPY ON)
