diff --git a/ec2-publish-ami b/ec2-publish-ami
index 721471f..2fc1b3f 100755
--- a/ec2-publish-ami
+++ b/ec2-publish-ami
@@ -84,6 +84,11 @@ if ! check4progs ec2-modify-image-attribute ; then
   exit 1
 fi
 
+if [ $# -lt 1 ] ; then
+  usage >&2
+  exit 1
+fi
+
 AMI_ID="$1"
 
 echo "Marking AMI $AMI_ID as public"
diff --git a/ec2-stop-instance b/ec2-stop-instance
index f542321..a8cad72 100755
--- a/ec2-stop-instance
+++ b/ec2-stop-instance
@@ -84,6 +84,11 @@ if ! check4progs ec2-stop-instances ; then
   exit 1
 fi
 
+if [ $# -lt 1 ] ; then
+  usage >&2
+  exit 1
+fi
+
 INSTANCE_ID="$1"
 
 echo "Stopping Instance ID $INSTANCE_ID"