diff --git a/check-linuxcnc-switchkins-remap-table.sh b/check-linuxcnc-switchkins-remap-table.sh
index 9357ad7..aa2c61b 100755
--- a/check-linuxcnc-switchkins-remap-table.sh
+++ b/check-linuxcnc-switchkins-remap-table.sh
@@ -380,6 +380,8 @@ validate_generator_cli_contract() {
     local cli_manifest_without_postgui
     local cli_manifest_without_remap
     local cli_manifest_without_tooldata
+    local cli_output_root_log
+    local cli_output_whitespace_log
     cli_dir=$(mktemp -d "${TMPDIR:-/tmp}/linuxcnc_switchkins_remap_cli.XXXXXX")
     trap 'rm -rf "$cli_dir"' EXIT
     cli_manifest="$cli_dir/bridgemill-manifest.txt"
@@ -408,6 +410,8 @@ validate_generator_cli_contract() {
     cli_manifest_without_postgui="$cli_dir/bridgemill-manifest-without-postgui.txt"
     cli_manifest_without_remap="$cli_dir/bridgemill-manifest-without-remap.txt"
     cli_manifest_without_tooldata="$cli_dir/bridgemill-manifest-without-tooldata.txt"
+    cli_output_root_log="$cli_dir/output-root.log"
+    cli_output_whitespace_log="$cli_dir/output-whitespace.log"
 
     if ! awk -F: -v manifest="$manifest_file" '
         function require(key) {
@@ -743,6 +747,29 @@ validate_generator_cli_contract() {
         exit 1
     fi
 
+    if LINUXCNC_ROOT="$linuxcnc_root" ./generate-linuxcnc-switchkins-remap-table.sh \
+        --all-output-dir "$cli_dir/out with space" "$cli_manifest" >"$cli_output_whitespace_log" 2>&1; then
+        echo "switchkins remap generator accepted an output directory with whitespace" >&2
+        exit 1
+    fi
+    if ! grep -F "switchkins remap output directory must not contain whitespace: $cli_dir/out with space" \
+        "$cli_output_whitespace_log" >/dev/null; then
+        echo "switchkins remap generator did not report whitespace output directories clearly" >&2
+        sed -n '1,20p' "$cli_output_whitespace_log" >&2
+        exit 1
+    fi
+    if LINUXCNC_ROOT="$linuxcnc_root" ./generate-linuxcnc-switchkins-remap-table.sh \
+        --all-output-dir / "$cli_manifest" >"$cli_output_root_log" 2>&1; then
+        echo "switchkins remap generator accepted the filesystem root as output directory" >&2
+        exit 1
+    fi
+    if ! grep -F "switchkins remap output directory must not be the filesystem root" \
+        "$cli_output_root_log" >/dev/null; then
+        echo "switchkins remap generator did not report filesystem-root output directories clearly" >&2
+        sed -n '1,20p' "$cli_output_root_log" >&2
+        exit 1
+    fi
+
     LINUXCNC_ROOT="$linuxcnc_root" ./generate-linuxcnc-switchkins-remap-table.sh --all-output-dir "$cli_dir/out" "$cli_manifest"
     LINUXCNC_ROOT="$linuxcnc_root" ./generate-linuxcnc-switchkins-remap-table.sh "$cli_manifest" \
         >"$cli_dir/linuxcnc_switchkins_remap_table.stdout.inc"
diff --git a/generate-linuxcnc-switchkins-remap-table.sh b/generate-linuxcnc-switchkins-remap-table.sh
index b9fdc45..130511f 100755
--- a/generate-linuxcnc-switchkins-remap-table.sh
+++ b/generate-linuxcnc-switchkins-remap-table.sh
@@ -64,6 +64,10 @@ if [[ "$mode" == all && -z "$all_output_dir" ]]; then
     echo "missing output directory for --all-output-dir" >&2
     exit 1
 fi
+if [[ "$mode" == all && "$all_output_dir" =~ [[:space:]] ]]; then
+    echo "switchkins remap output directory must not contain whitespace: $all_output_dir" >&2
+    exit 1
+fi
 
 linuxcnc_root=$(cd "$linuxcnc_root" && pwd)
 
@@ -1244,6 +1248,11 @@ elif [[ "$mode" == all ]]; then
         exit 1
     fi
     mkdir -p "$all_output_dir"
+    all_output_dir=$(cd "$all_output_dir" && pwd)
+    if [[ "$all_output_dir" == "/" ]]; then
+        echo "switchkins remap output directory must not be the filesystem root" >&2
+        exit 1
+    fi
     write_generated_file "$all_output_dir/linuxcnc_switchkins_remap_table.inc" "table" write_table
     write_generated_file "$all_output_dir/linuxcnc_switchkins_remap_config_cases.inc" "config cases" write_config_cases
     write_generated_file "$all_output_dir/linuxcnc_switchkins_remap_config_cases.json" "JSON config cases" write_json_cases