diff --git a/railway-gauge.json b/railway-gauge.json
index 090a5d0..da217cb 100644
--- a/railway-gauge.json
+++ b/railway-gauge.json
@@ -24,38 +24,43 @@
         "styles": "{% if gauges|length < 2 %}default{% else %}{% for i, v in gauges %}{% if i != 0 %},{% endif %}gauge{{ i }}{% endfor %}{% endif %}",
         "style": {
             "width": "3",
-            "color": "{% if tags.gauge %}{{ colorInterpolate([ '#00ff00', '#0000ff' ], gauges[0] / 2000) }}{% else %}#404040{% endif %}"
+            "color": "{% if tags.gauge %}{% if not tags.gauge|matches('^\\d+$') %}#ff0000{% else %}{{ colorInterpolate([ '#00ff00', '#0000ff' ], tags.gauge / 2000) }}{% endif %}{% else %}#404040{% endif %}"
         },
         "style:gauge0": {
             "width": "3",
             "lineCap": "butt",
-            "color": "{{ colorInterpolate([ '#00ff00', '#0000ff' ], gauges[0] / 2000) }}",
+            "color": "{% if not gauges[0]|matches('^[0-9]+$') %}#ff0000{% else %}{{ colorInterpolate([ '#00ff00', '#0000ff' ], gauges[0] / 2000) }}{% endif %}",
             "dashArray": "5,{{ (gauges|length - 1) * 5 }}"
         },
         "style:gauge1": {
             "width": "3",
             "lineCap": "butt",
-            "color": "{{ colorInterpolate([ '#00ff00', '#0000ff' ], gauges[1] / 2000) }}",
+            "color": "{% if not gauges[1]|matches('^[0-9]+$') %}#ff0000{% else %}{{ colorInterpolate([ '#00ff00', '#0000ff' ], gauges[1] / 2000) }}{% endif %}",
             "dashArray": "5,{{ (gauges|length - 1) * 5 }}",
             "dashOffset": "5"
         },
         "style:gauge2": {
             "width": "3",
             "lineCap": "butt",
-            "color": "{{ colorInterpolate([ '#00ff00', '#0000ff' ], gauges[2] / 2000) }}",
+            "color": "{% if not gauges[2]|matches('^\\d+$') %}#ff0000{% else %}{{ colorInterpolate([ '#00ff00', '#0000ff' ], gauges[2] / 2000) }}{% endif %}",
             "dashArray": "5,{{ (gauges|length - 1) * 5 }}",
             "dashOffset": "10"
         },
         "style:gauge3": {
             "width": "3",
             "lineCap": "butt",
-            "color": "{{ colorInterpolate([ '#00ff00', '#0000ff' ], gauges[3] / 2000) }}",
+            "color": "{% if not gauges[3]|matches('^\\d+$') %}#ff0000{% else %}{{ colorInterpolate([ '#00ff00', '#0000ff' ], gauges[3] / 2000) }}{% endif %}",
             "dashArray": "5,{{ (gauges|length - 1) * 5 }}",
             "dashOffset": "15"
         }
     },
     "info": [
         "<table>",
+        "  {% set color = '#ff0000' %}",
+        "  <tr>",
+        "    <td>{{ markerLine({ 'width': 3, 'color': color })|raw }}</td>",
+        "    <td>{{ trans('illegal value') }}</td>",
+        "  </tr>",
         "  {% set color = '#404040' %}",
         "  <tr>",
         "    <td>{{ markerLine({ 'width': 3, 'color': color })|raw }}</td>",