diff --git a/src/css/codemirror.css b/src/css/codemirror.css
index 9b78ca221..61c7b1fde 100644
--- a/src/css/codemirror.css
+++ b/src/css/codemirror.css
@@ -26,6 +26,12 @@
 .cm-s-default .cm-string-2 { color: #930; }
 .cm-s-default .cm-comment { color: #777; }
 .cm-s-default .cm-keyword { color: #90b; }
+.cm-s-default .cm-regex {
+    text-underline-position: under;
+    text-decoration-color: darkgray;
+    text-decoration-style: solid;
+    text-decoration-line: underline;
+    }
 .cm-s-default .cm-error,
 .CodeMirror-linebackground.error {
     background-color: #ff000018;
diff --git a/src/js/codemirror/ubo-static-filtering.js b/src/js/codemirror/ubo-static-filtering.js
index 6b2173dd0..999b545c0 100644
--- a/src/js/codemirror/ubo-static-filtering.js
+++ b/src/js/codemirror/ubo-static-filtering.js
@@ -104,11 +104,17 @@ CodeMirror.defineMode("ubo-static-filtering", function() {
             parserSlot >= parser.patternSpan.i &&
             parserSlot < parser.patternRightAnchorSpan.i
         ) {
-            if ( (parser.slices[parserSlot] & (parser.BITAsterisk | parser.BITCaret)) !== 0 ) {
+            const isRegex = parser.patternIsRegex();
+            if (
+                (isRegex === false) &&
+                (parser.slices[parserSlot] & (parser.BITAsterisk | parser.BITCaret)) !== 0
+            ) {
                 stream.pos += parser.slices[parserSlot+2];
                 parserSlot += 3;
                 return 'keyword strong';
             }
+            let style = 'variable';
+            if ( isRegex ) { style += ' regex'; }
             const nextSlot = parser.skipUntil(
                 parserSlot,
                 parser.patternRightAnchorSpan.i,
@@ -116,7 +122,7 @@ CodeMirror.defineMode("ubo-static-filtering", function() {
             );
             stream.pos = parser.slices[nextSlot+1];
             parserSlot = nextSlot;
-            return 'variable';
+            return style;
         }
         if (
             parserSlot === parser.optionsAnchorSpan.i &&
diff --git a/src/js/static-filtering-parser.js b/src/js/static-filtering-parser.js
index a61801872..93bbd0457 100644
--- a/src/js/static-filtering-parser.js
+++ b/src/js/static-filtering-parser.js
@@ -350,11 +350,10 @@ const Parser = class {
                     // https://github.com/gorhill/uBlock/issues/952
                     //   AdGuard-specific `$$` filters => unsupported.
                     if ( this.findFirstOdd(0, BITHostname | BITComma | BITAsterisk) === i ) {
+                        this.flavorBits |= BITFlavorError;
                         if ( this.interactive ) {
                             this.markSlices(i, i+3, BITError);
                         }
-                        this.allBits |= BITError;
-                        this.flavorBits |= BITFlavorError;
                     } else {
                         this.splitSlot(i, l - 1);
                         i += 3;
@@ -568,8 +567,7 @@ const Parser = class {
                 void new RegExp(this.getNetPattern());
             }
             catch (ex) {
-                const { i, l } = this.patternSpan;
-                this.markSlices(i, i + l, BITError);
+                this.markSpan(this.patternSpan, BITError);
             }
         } else if ( this.patternIsDubious() ) {
             this.markSpan(this.patternSpan, BITError);
@@ -979,7 +977,7 @@ const Parser = class {
     }
 
     hasError() {
-        return hasBits(this.allBits, BITError);
+        return hasBits(this.flavorBits, BITFlavorError);
     }
 };