diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8cf0d0587240..20d0eced0bcb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Remove `autoprefixer` dependency ([#11315](https://github.com/tailwindlabs/tailwindcss/pull/11315))
 - Fix source maps issue resulting in a crash ([#11319](https://github.com/tailwindlabs/tailwindcss/pull/11319))
 - Fallback to RegEx based parser when using custom transformers or extractors ([#11335](https://github.com/tailwindlabs/tailwindcss/pull/11335))
+- Move unknown pseudo-elements outside of `:is` by default ([#11345](https://github.com/tailwindlabs/tailwindcss/pull/11345))
 
 ### Added
 
diff --git a/src/util/pseudoElements.js b/src/util/pseudoElements.js
index 30466ec2ca36..5795cdd42045 100644
--- a/src/util/pseudoElements.js
+++ b/src/util/pseudoElements.js
@@ -19,12 +19,13 @@
 // **Jumpable**
 // Any terminal element may "jump" over combinators when moving to the end of the selector
 //
-// This is a backwards-compat quirk of :before and :after variants.
+// This is a backwards-compat quirk of pseudo element variants from earlier versions of Tailwind CSS.
 
 /** @typedef {'terminal' | 'actionable' | 'jumpable'} PseudoProperty */
 
 /** @type {Record<string, PseudoProperty[]>} */
 let elementProperties = {
+  // Pseudo elements from the spec
   '::after': ['terminal', 'jumpable'],
   '::backdrop': ['terminal', 'jumpable'],
   '::before': ['terminal', 'jumpable'],
@@ -41,18 +42,14 @@ let elementProperties = {
   '::spelling-error': ['terminal'],
   '::target-text': ['terminal'],
 
-  // other
+  // Pseudo elements from the spec with special rules
   '::file-selector-button': ['terminal', 'actionable'],
-  '::-webkit-progress-bar': ['terminal', 'actionable'],
 
-  // Webkit scroll bar pseudo elements can be combined with user-action pseudo classes
-  '::-webkit-scrollbar': ['terminal', 'actionable'],
-  '::-webkit-scrollbar-button': ['terminal', 'actionable'],
-  '::-webkit-scrollbar-thumb': ['terminal', 'actionable'],
-  '::-webkit-scrollbar-track': ['terminal', 'actionable'],
-  '::-webkit-scrollbar-track-piece': ['terminal', 'actionable'],
-  '::-webkit-scrollbar-corner': ['terminal', 'actionable'],
-  '::-webkit-resizer': ['terminal', 'actionable'],
+  // Library-specific pseudo elements used by component libraries
+  // These are Shadow DOM-like
+  '::deep': ['actionable'],
+  '::v-deep': ['actionable'],
+  '::ng-deep': ['actionable'],
 
   // Note: As a rule, double colons (::) should be used instead of a single colon
   // (:). This distinguishes pseudo-classes from pseudo-elements. However, since
@@ -65,8 +62,8 @@ let elementProperties = {
 
   // The default value is used when the pseudo-element is not recognized
   // Because it's not recognized, we don't know if it's terminal or not
-  // So we assume it can't be moved AND can have user-action pseudo classes attached to it
-  __default__: ['actionable'],
+  // So we assume it can be moved AND can have user-action pseudo classes attached to it
+  __default__: ['terminal', 'actionable'],
 }
 
 /**
diff --git a/tests/util/apply-important-selector.test.js b/tests/util/apply-important-selector.test.js
index ab9842d838c9..0622d802e3ab 100644
--- a/tests/util/apply-important-selector.test.js
+++ b/tests/util/apply-important-selector.test.js
@@ -16,6 +16,10 @@ it.each`
   ${':is(.foo) :is(.bar)'}                      | ${'#app :is(:is(.foo) :is(.bar))'}
   ${':is(.foo)::before'}                        | ${'#app :is(.foo)::before'}
   ${'.foo:before'}                              | ${'#app :is(.foo):before'}
+  ${'.foo::some-uknown-pseudo'}                 | ${'#app :is(.foo)::some-uknown-pseudo'}
+  ${'.foo::some-uknown-pseudo:hover'}           | ${'#app :is(.foo)::some-uknown-pseudo:hover'}
+  ${'.foo:focus::some-uknown-pseudo:hover'}     | ${'#app :is(.foo:focus)::some-uknown-pseudo:hover'}
+  ${'.foo:hover::some-uknown-pseudo:focus'}     | ${'#app :is(.foo:hover)::some-uknown-pseudo:focus'}
 `('should generate "$after" from "$before"', ({ before, after }) => {
   expect(applyImportantSelector(before, '#app')).toEqual(after)
 })