diff --git a/README.rst b/README.rst
index 3b19d62a8816c2dd30a9df77de7a2d6b424eedb7..6a25974de2a4f96030ace4d94c1ee7250cee1328 100644
--- a/README.rst
+++ b/README.rst
@@ -63,8 +63,3 @@ Simply run:
 .. code:: shell
 
     make test
-
-TODO
-----
-
-- Detect when no parameters are passed and output a usage message.
diff --git a/bundle_certs b/bundle_certs
index 9d14d93486437b794fe9b498076a0d2309f4b950..0c21a09fbe7bd01bb98fa971911f8de79cf1a17f 100755
--- a/bundle_certs
+++ b/bundle_certs
@@ -78,4 +78,10 @@ bundle_certs () {
     rm -r certs
 }
 
+
+if [ ! "$sourced" ] && [ $# -eq 0 ]
+then
+    echo "Usage: $0 filename [filename2 [filename3 ...]]" > /dev/stderr
+    exit 1
+fi
 [ ! "$sourced" ] && bundle_certs "$@"