diff --git a/platform/npm/tests/snfe.js b/platform/npm/tests/snfe.js
index f0ee86b57..b1cee181c 100644
--- a/platform/npm/tests/snfe.js
+++ b/platform/npm/tests/snfe.js
@@ -341,6 +341,31 @@ describe('SNFE', () => {
                     });
                     assert.strictEqual(r, 0);
                 });
+
+                // https://github.com/AdguardTeam/AdguardFilters/issues/88067#issuecomment-1019518277
+                it('should match regex-based filter without `match-case` option', async () => {
+                    await engine.useLists([
+                        { name: 'test', raw: '/\.com\/[a-z]{9,}\/[a-z]{9,}\.js$/$script,1p' },
+                    ]);
+                    const r = engine.matchRequest({
+                        originURL: 'https://example.com/',
+                        type: 'script',
+                        url: 'https://example.com/LQMDQSMLDAZAEHERE/LQMDQSMLDAZAEHERE.js',
+                    });
+                    assert.strictEqual(r, 1);
+                });
+
+                it('should not match regex-based filter with `match-case` option', async () => {
+                    await engine.useLists([
+                        { name: 'test', raw: '/\.com\/[a-z]{9,}\/[a-z]{9,}\.js$/$script,1p,match-case' },
+                    ]);
+                    const r = engine.matchRequest({
+                        originURL: 'https://example.com/',
+                        type: 'script',
+                        url: 'https://example.com/LQMDQSMLDAZAEHERE/LQMDQSMLDAZAEHERE.js',
+                    });
+                    assert.strictEqual(r, 0);
+                });
             });
         });
     }
diff --git a/src/js/static-net-filtering.js b/src/js/static-net-filtering.js
index e96bb8b82..f28c6ca10 100644
--- a/src/js/static-net-filtering.js
+++ b/src/js/static-net-filtering.js
@@ -1108,7 +1108,7 @@ const FilterRegex = class {
         if ( refs.$re === null ) {
             refs.$re = new RegExp(
                 this.getRegexPattern(idata),
-                filterData[idata+3] === 0 ? '' : 'i'
+                filterData[idata+3] === 0 ? 'i' : ''
             );
         }
         if ( refs.$re.test($requestURLRaw) === false ) { return false; }