diff --git a/fixup-yaml.sh b/fixup-yaml.sh
new file mode 100644
index 00000000..ac4a7915
--- /dev/null
+++ b/fixup-yaml.sh
@@ -0,0 +1,16 @@
+#!/bin/sh
+# Some tools will choke on the YAML files generated by PyYAML;
+# in particular on a section like this one:
+#
+# service:
+#   ports:
+#   - 8000:5000
+#
+# This script adds two spaces in front of the dash in those files.
+# Warning: it is a hack, and probably won't work on some YAML files.
+[ -f "$COMPOSE_FILE" ] || {
+    echo "Cannot find COMPOSE_FILE"
+    exit 1
+}
+sed -i 's/^  -/    -/' $COMPOSE_FILE
+