diff --git a/tools/fail_if_no_c.py b/tools/fail_if_no_c.py
new file mode 100644
index 000000000..96afa0448
--- /dev/null
+++ b/tools/fail_if_no_c.py
@@ -0,0 +1,26 @@
+# Copyright 2009 10gen, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Fail if the C extension module doesn't exist.
+
+Only really intended to be used by internal build scripts.
+"""
+
+import sys
+sys.path[0:0] = [""]
+
+try:
+    from pymongo import _cbson
+except ImportError:
+    sys.exit("could not import _cbson")