diff --git a/manage.sh b/manage.sh
index 404acd11..a166e3b7 100755
--- a/manage.sh
+++ b/manage.sh
@@ -33,6 +33,10 @@ function bump {
     previousVersion=$( grep '^version =' setup.py | sed 's/version = \"\(.*\)\"/\1/' )
     echo "Next version number? (previous: '$previousVersion')"
     read version
+    if [ -z "$version" ]; then
+        echo "empty version string"
+        exit 1
+    fi
     sed -i -b "s/version = .*/version = \"$version\"/" setup.py
 }