diff --git a/src/js/codemirror/ubo-static-filtering.js b/src/js/codemirror/ubo-static-filtering.js
index 656aaa0c1..1c268647a 100644
--- a/src/js/codemirror/ubo-static-filtering.js
+++ b/src/js/codemirror/ubo-static-filtering.js
@@ -177,6 +177,56 @@ CodeMirror.defineMode('ubo-static-filtering', function() {
         return null;
     };
 
+    const colorNetOptionValueSpan = function(stream, bits) {
+        const { pos, string } = stream;
+        let style;
+        // Warn about unknown redirect tokens.
+        if (
+            string.charCodeAt(pos - 1) === 0x3D /* '=' */ &&
+            /[$,]redirect(-rule)?=$/.test(string.slice(0, pos))
+        ) {
+            style = 'value';
+            let end = parser.skipUntil(
+                parserSlot,
+                parser.commentSpan.i,
+                parser.BITComma
+            );
+            const token = parser.strFromSlices(parserSlot, end - 3);
+            if ( redirectNames.has(token) === false ) {
+                style += ' warning';
+            }
+            stream.pos += token.length;
+            parserSlot = end;
+            return style;
+        }
+        if ( (bits & parser.BITTilde) !== 0 ) {
+            style = 'keyword strong';
+        } else if ( (bits & parser.BITPipe) !== 0 ) {
+            style = 'def';
+        }
+        stream.pos += parser.slices[parserSlot+2];
+        parserSlot += 3;
+        return style || 'value';
+    };
+
+    const colorNetOptionSpan = function(stream) {
+        const bits = parser.slices[parserSlot];
+        let style;
+        if ( (bits & parser.BITComma) !== 0  ) {
+            style = 'def strong';
+            netOptionValueMode = false;
+        } else if ( netOptionValueMode ) {
+            return colorNetOptionValueSpan(stream, bits);
+        } else if ( (bits & parser.BITTilde) !== 0 ) {
+            style = 'keyword strong';
+        } else if ( (bits & parser.BITEqual) !== 0 ) {
+            netOptionValueMode = true;
+        }
+        stream.pos += parser.slices[parserSlot+2];
+        parserSlot += 3;
+        return style || 'def';
+    };
+
     const colorNetSpan = function(stream) {
         if ( parserSlot < parser.exceptionSpan.i ) {
             stream.pos += parser.slices[parserSlot+2];
@@ -236,23 +286,7 @@ CodeMirror.defineMode('ubo-static-filtering', function() {
             parserSlot >= parser.optionsSpan.i &&
             parserSlot < parser.commentSpan.i
         ) {
-            const bits = parser.slices[parserSlot];
-            let style;
-            if ( (bits & parser.BITComma) !== 0  ) {
-                style = 'def strong';
-                netOptionValueMode = false;
-            } else if ( (bits & parser.BITTilde) !== 0 ) {
-                style = 'keyword strong';
-            } else if ( (bits & parser.BITPipe) !== 0 ) {
-                style = 'def';
-            } else if ( netOptionValueMode ) {
-                style = 'value';
-            } else if ( (bits & parser.BITEqual) !== 0 ) {
-                netOptionValueMode = true;
-            }
-            stream.pos += parser.slices[parserSlot+2];
-            parserSlot += 3;
-            return style || 'def';
+            return colorNetOptionSpan(stream);
         }
         if (
             parserSlot >= parser.commentSpan.i &&