diff --git a/build-scripts/clean-buildmachine b/build-scripts/clean-buildmachine
index 31d0c51d2..e5104e719 100755
--- a/build-scripts/clean-buildmachine
+++ b/build-scripts/clean-buildmachine
@@ -1,15 +1,27 @@
 #!/bin/sh
 
-. `dirname "$0"`/functions
+# This script cleans a build machine by uninstalling cfbuild and removing the
+# contents of the PREFIX directory.
+#
+# Don't run this script on your dev machine! You may accidentally delete
+# something very important.
+
+. "$(dirname "$0")"/functions
 . detect-environment
 
 uninstall_cfbuild
 
+if [ -z "$PREFIX" ] || [ "$PREFIX" = "/" ]; then
+    echo "$(basename "$0"): Error: \$PREFIX is not defined, is empty, or is set to the root directory. Aborting to prevent accidental deletion."
+    exit 1
+fi
+
+echo "$(basename "$0"): Debug: Cleaning build host by deleting $PREFIX"
 case $OS in
-aix)
-sudo rm -rf "$PREFIX"/*
-;;
-*)
-sudo rm -rf "$PREFIX"
-;;
+    aix)
+        sudo rm -rf "$PREFIX"/*
+        ;;
+    *)
+        sudo rm -rf "$PREFIX"
+        ;;
 esac