diff --git a/boilerplate/make-cairo-boilerplate-constructors.sh b/boilerplate/make-cairo-boilerplate-constructors.sh
index 2c7fc85e8..dd6311178 100644
--- a/boilerplate/make-cairo-boilerplate-constructors.sh
+++ b/boilerplate/make-cairo-boilerplate-constructors.sh
@@ -1,4 +1,9 @@
-#!/bin/sh
+#! /bin/sh
+
+if test $# == 0; then
+    echo "$0: no input files." >&2
+    exit 0
+fi
 
 cat <<HERE
 /* WARNING: Autogenerated file - see $0! */
diff --git a/test/make-cairo-test-constructors.sh b/test/make-cairo-test-constructors.sh
index d0325e876..fdb84e9dc 100644
--- a/test/make-cairo-test-constructors.sh
+++ b/test/make-cairo-test-constructors.sh
@@ -1,4 +1,9 @@
-#!/bin/sh
+#! /bin/sh
+
+if test $# == 0; then
+    echo "$0: no input files." >&2
+    exit 0
+fi
 
 cat <<HERE
 /* WARNING: Autogenerated file - see $0! */