diff --git a/phpBB/phpbb/assets/iconify_bundler.php b/phpBB/phpbb/assets/iconify_bundler.php
index 2671cb0880..9bda03695c 100644
--- a/phpBB/phpbb/assets/iconify_bundler.php
+++ b/phpBB/phpbb/assets/iconify_bundler.php
@@ -47,22 +47,26 @@ class iconify_bundler
 		$organized_icons = $this->organize_icons_list();
 
 		$output = $this->load_icons_data($organized_icons);
+		if (!$output)
+		{
+			return '';
+		}
 
 		$output = '(function() {
-   function add(data) {
-       try {
-           if (typeof self.Iconify === \'object\' && self.Iconify.addCollection) {
-               self.Iconify.addCollection(data);
-               return;
-           }
-           if (typeof self.IconifyPreload === \'undefined\') {
-               self.IconifyPreload = [];
-           }
-           self.IconifyPreload.push(data);
-       } catch (err) {
-       }
-   }
-   ' . $output . '
+    function add(data) {
+        try {
+            if (typeof self.Iconify === \'object\' && self.Iconify.addCollection) {
+                self.Iconify.addCollection(data);
+                return;
+            }
+            if (typeof self.IconifyPreload === \'undefined\') {
+                self.IconifyPreload = [];
+            }
+            self.IconifyPreload.push(data);
+        } catch (err) {
+        }
+    }
+    ' . $output . '
 })();' . "\n";
 
 		return $output;
@@ -111,7 +115,7 @@ class iconify_bundler
 		{
 			// Split icon to prefix and name
 			$icon = $this->name_to_icon($icon_name);
-			if ($icon === null || $icon['provider'] !== '')
+			if ($icon === null)
 			{
 				// Invalid name or icon name does not have provider
 				if ($this->log)
@@ -216,24 +220,20 @@ class iconify_bundler
 		{
 			// Load icon set
 			$collection = new Collection($prefix);
-			if (!$collection->loadIconifyCollection($prefix))
+			$collection_file = Collection::findIconifyCollection($prefix);
+			if (!file_exists($collection_file) || !$collection->loadFromFile($collection_file))
 			{
-				if ($this->log)
-				{
-					$this->log->add('critical', ANONYMOUS, '', 'LOG_ICON_COLLECTION_INVALID', false, [$prefix]);
-				}
+				$this->log?->add('critical', ANONYMOUS, '', 'LOG_ICON_COLLECTION_INVALID', false, [$prefix]);
 				continue;
 			}
 
 			// Make sure all icons exist
-			foreach ($iconsList as $name)
+			foreach ($iconsList as $key => $name)
 			{
 				if (!$collection->iconExists($name))
 				{
-					if ($this->log)
-					{
-						$this->log->add('critical', ANONYMOUS, '', 'LOG_ICON_INVALID', false, [$prefix . ':' . $name]);
-					}
+					$this->log?->add('critical', ANONYMOUS, '', 'LOG_ICON_INVALID', false, [$prefix . ':' . $name]);
+					unset($iconsList[$key]);
 				}
 			}
 
diff --git a/tests/assets/iconify_bundler_tests.php b/tests/assets/iconify_bundler_tests.php
new file mode 100644
index 0000000000..d2d9c01a6c
--- /dev/null
+++ b/tests/assets/iconify_bundler_tests.php
@@ -0,0 +1,141 @@
+<?php
+/**
+ *
+ * This file is part of the phpBB Forum Software package.
+ *
+ * @copyright (c) phpBB Limited <https://www.phpbb.com>
+ * @license GNU General Public License, version 2 (GPL-2.0)
+ *
+ * For full copyright and license information, please see
+ * the docs/CREDITS.txt file.
+ *
+ */
+
+namespace phpbb\tests\unit\assets;
+
+class iconify_bundler_tests extends \phpbb_test_case
+{
+	/** @var array Log content */
+	protected $log_content = [];
+
+	/** @var \phpbb\assets\iconify_bundler */
+	protected $bundler;
+
+	public function setUp(): void
+	{
+		$log = $this->getMockBuilder('\phpbb\log\dummy')
+			->onlyMethods(['add'])
+			->getMock();
+		$log->method('add')
+			->willReturnCallback(function ($mode, $user_id, $log_ip, $log_operation, $log_time = false, $additional_data = array()) {
+				$this->log_content[] = $log_operation;
+			});
+
+		$this->bundler = new \phpbb\assets\iconify_bundler($log);
+	}
+
+	public function data_test_generate_bundle()
+	{
+		return [
+			[
+				['fa:address-card-o'],
+				['"prefix":"fa"', '"address-card-o"'],
+			],
+			[
+				['fa:address-card-o', 'fa-regular:credit-card'],
+				['"prefix":"fa"', '"address-card-o"', '"prefix":"fa-regular"', '"credit-card"'],
+			],
+			[
+				['fa:address-card-o', 'fa:foo-bar'],
+				['"prefix":"fa"', '"address-card-o"'],
+				['LOG_ICON_INVALID'],
+			],
+			[
+				['fa:address-card-o', 'fa-regular:credit-card', 'fa-regular:credit-card'],
+				['"prefix":"fa"', '"address-card-o"', '"prefix":"fa-regular"', '"credit-card"'],
+			],
+			[
+				['fa:address-card-o', 'fa-regular:credit-card', 'fa-regular:angry'],
+				['"prefix":"fa"', '"address-card-o"', '"prefix":"fa-regular"', '"credit-card"', '"angry"'],
+			],
+			[
+				['fa:address-card-o', 'fa:bell', 'fa-regular:credit-card', 'fa-regular:angry'],
+				['"prefix":"fa"', '"address-card-o"', '"bell"', '"prefix":"fa-regular"', '"credit-card"', '"angry"'],
+			],
+			[
+				['@test'],
+				[],
+				['LOG_ICON_INVALID'],
+			],
+			[
+				['fa:address-foo-o'],
+				['"prefix":"fa"', '"icons":[]'],
+				['LOG_ICON_INVALID'],
+			],
+			[
+				['foo:bar'],
+				[],
+				['LOG_ICON_COLLECTION_INVALID']
+			],
+			[
+				['@iconify:fa:address-card-o'],
+				['"prefix":"fa"', '"address-card-o"'],
+			],
+			[
+				['@iconify:someother:fa:address-card-o'],
+				[],
+				['LOG_ICON_INVALID'],
+			],
+			[
+				['iconify:fa:address-card-o'],
+				['"prefix":"fa"', '"address-card-o"'],
+			],
+			[
+				['iconify:fa:fa:address-card-o'],
+				[],
+				['LOG_ICON_INVALID'],
+			],
+			[
+				['test'],
+				[],
+				['LOG_ICON_INVALID'],
+			],
+			[
+				[''],
+				[],
+				['LOG_ICON_INVALID'],
+			],
+			[
+				['fa-address-card-o'],
+				['"prefix":"fa"', '"address-card-o"'],
+			],
+		];
+	}
+
+	/**
+	 * @dataProvider data_test_generate_bundle
+	 */
+	public function test_generate_bundle($icons, $expected, $log_content = [])
+	{
+		$this->bundler->add_icons($icons);
+		$bundle = $this->bundler->run();
+		foreach ($expected as $expected_part)
+		{
+			$this->assertStringContainsString($expected_part, $bundle, 'Failed asserting that generated bundle contains ' . $expected_part);
+		}
+
+		if (!count($expected))
+		{
+			$this->assertEquals($bundle, '', 'Failed asserting that generated bundle is empty');
+		}
+
+		if (count($log_content))
+		{
+			$this->assertEquals($this->log_content, $log_content, 'Failed asserting that log content is correct');
+		}
+		else
+		{
+			$this->assertEmpty($this->log_content, 'Failed asserting that log content is empty');
+		}
+	}
+}