diff --git a/packages/block-editor/src/components/color-style-selector/index.js b/packages/block-editor/src/components/color-style-selector/index.js
index 957e3adc400e6..4a76a1da8369e 100644
--- a/packages/block-editor/src/components/color-style-selector/index.js
+++ b/packages/block-editor/src/components/color-style-selector/index.js
@@ -13,7 +13,7 @@ import { DOWN } from '@wordpress/keycodes';
 import deprecated from '@wordpress/deprecated';
 
 const ColorSelectorSVGIcon = () => (
-	<SVG xmlns="https://www.w3.org/2000/svg" viewBox="0 0 20 20">
+	<SVG xmlns="http://www.w3.org/2000/svg" viewBox="0 0 20 20">
 		<Path d="M7.434 5l3.18 9.16H8.538l-.692-2.184H4.628l-.705 2.184H2L5.18 5h2.254zm-1.13 1.904h-.115l-1.148 3.593H7.44L6.304 6.904zM14.348 7.006c1.853 0 2.9.876 2.9 2.374v4.78h-1.79v-.914h-.114c-.362.64-1.123 1.022-2.031 1.022-1.346 0-2.292-.826-2.292-2.108 0-1.27.972-2.006 2.71-2.107l1.696-.102V9.38c0-.584-.42-.914-1.18-.914-.667 0-1.112.228-1.264.647h-1.701c.12-1.295 1.307-2.107 3.066-2.107zm1.079 4.1l-1.416.09c-.793.056-1.18.342-1.18.844 0 .52.45.837 1.091.837.857 0 1.505-.545 1.505-1.256v-.515z" />
 	</SVG>
 );
diff --git a/packages/icons/CHANGELOG.md b/packages/icons/CHANGELOG.md
index 3a4df4e364c85..7ce0c1bbfa3ff 100644
--- a/packages/icons/CHANGELOG.md
+++ b/packages/icons/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Bug Fix
+
+-   Fixed invalid XML namespace on `alignJustify`, `customLink`, `mapMarker`, `postContent` and `title` ([#53955](https://github.com/WordPress/gutenberg/pull/53955)).
+
 ## 9.31.0 (2023-08-16)
 
 ## 9.30.0 (2023-08-10)
diff --git a/packages/icons/src/library/align-justify.js b/packages/icons/src/library/align-justify.js
index 9fee191c0a71e..f79a8bf06d5b2 100644
--- a/packages/icons/src/library/align-justify.js
+++ b/packages/icons/src/library/align-justify.js
@@ -4,7 +4,7 @@
 import { SVG, Path } from '@wordpress/primitives';
 
 const alignJustify = (
-	<SVG xmlns="https://www.w3.org/2000/svg" viewBox="0 0 24 24">
+	<SVG xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24">
 		<Path d="M4 12.8h16v-1.5H4v1.5zm0 7h12.4v-1.5H4v1.5zM4 4.3v1.5h16V4.3H4z" />
 	</SVG>
 );
diff --git a/packages/icons/src/library/custom-link.js b/packages/icons/src/library/custom-link.js
index 27a5d24a71083..b7aa7c309aaeb 100644
--- a/packages/icons/src/library/custom-link.js
+++ b/packages/icons/src/library/custom-link.js
@@ -4,7 +4,7 @@
 import { SVG, Path } from '@wordpress/primitives';
 
 const customLink = (
-	<SVG xmlns="https://www.w3.org/2000/svg" viewBox="0 0 24 24">
+	<SVG xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24">
 		<Path d="M12.5 14.5h-1V16h1c2.2 0 4-1.8 4-4s-1.8-4-4-4h-1v1.5h1c1.4 0 2.5 1.1 2.5 2.5s-1.1 2.5-2.5 2.5zm-4 1.5v-1.5h-1C6.1 14.5 5 13.4 5 12s1.1-2.5 2.5-2.5h1V8h-1c-2.2 0-4 1.8-4 4s1.8 4 4 4h1zm-1-3.2h5v-1.5h-5v1.5zM18 4H9c-1.1 0-2 .9-2 2v.5h1.5V6c0-.3.2-.5.5-.5h9c.3 0 .5.2.5.5v12c0 .3-.2.5-.5.5H9c-.3 0-.5-.2-.5-.5v-.5H7v.5c0 1.1.9 2 2 2h9c1.1 0 2-.9 2-2V6c0-1.1-.9-2-2-2z" />
 	</SVG>
 );
diff --git a/packages/icons/src/library/map-marker.js b/packages/icons/src/library/map-marker.js
index f142d17d352af..52fa68e9590c3 100644
--- a/packages/icons/src/library/map-marker.js
+++ b/packages/icons/src/library/map-marker.js
@@ -4,7 +4,7 @@
 import { SVG, Path } from '@wordpress/primitives';
 
 const mapMarker = (
-	<SVG xmlns="https://www.w3.org/2000/svg" viewBox="0 0 24 24">
+	<SVG xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24">
 		<Path d="M12 9c-.8 0-1.5.7-1.5 1.5S11.2 12 12 12s1.5-.7 1.5-1.5S12.8 9 12 9zm0-5c-3.6 0-6.5 2.8-6.5 6.2 0 .8.3 1.8.9 3.1.5 1.1 1.2 2.3 2 3.6.7 1 3 3.8 3.2 3.9l.4.5.4-.5c.2-.2 2.6-2.9 3.2-3.9.8-1.2 1.5-2.5 2-3.6.6-1.3.9-2.3.9-3.1C18.5 6.8 15.6 4 12 4zm4.3 8.7c-.5 1-1.1 2.2-1.9 3.4-.5.7-1.7 2.2-2.4 3-.7-.8-1.9-2.3-2.4-3-.8-1.2-1.4-2.3-1.9-3.3-.6-1.4-.7-2.2-.7-2.5 0-2.6 2.2-4.7 5-4.7s5 2.1 5 4.7c0 .2-.1 1-.7 2.4z" />
 	</SVG>
 );
diff --git a/packages/icons/src/library/post-content.js b/packages/icons/src/library/post-content.js
index 4f9d6ce56ed83..6047a5ad368f6 100644
--- a/packages/icons/src/library/post-content.js
+++ b/packages/icons/src/library/post-content.js
@@ -4,7 +4,7 @@
 import { SVG, Path } from '@wordpress/primitives';
 
 const postContent = (
-	<SVG xmlns="https://www.w3.org/2000/svg" viewBox="0 0 24 24">
+	<SVG xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24">
 		<Path d="M4 6h12V4.5H4V6Zm16 4.5H4V9h16v1.5ZM4 15h16v-1.5H4V15Zm0 4.5h16V18H4v1.5Z" />
 	</SVG>
 );
diff --git a/packages/icons/src/library/title.js b/packages/icons/src/library/title.js
index d70f2fd52f619..cf77753bc35f8 100644
--- a/packages/icons/src/library/title.js
+++ b/packages/icons/src/library/title.js
@@ -4,7 +4,7 @@
 import { SVG, Path } from '@wordpress/primitives';
 
 const title = (
-	<SVG xmlns="https://www.w3.org/2000/svg" viewBox="0 0 24 24">
+	<SVG xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24">
 		<Path d="m4 5.5h2v6.5h1.5v-6.5h2v-1.5h-5.5zm16 10.5h-16v-1.5h16zm-7 4h-9v-1.5h9z" />
 	</SVG>
 );