diff --git a/src/Psalm/Config.php b/src/Psalm/Config.php
index d9fadf20fae..a65deb91270 100644
--- a/src/Psalm/Config.php
+++ b/src/Psalm/Config.php
@@ -72,6 +72,7 @@
 use function implode;
 use function in_array;
 use function is_a;
+use function is_array;
 use function is_dir;
 use function is_file;
 use function is_string;
@@ -595,6 +596,13 @@ class Config
         "xdebug" => false,
     ];
 
+    /**
+     * A list of php extensions required by the project that aren't fully supported by Psalm.
+     *
+     * @var array<string, true>
+     */
+    public $php_extensions_not_supported = [];
+
     /**
      * @var array<class-string, PluginInterface>
      */
@@ -995,12 +1003,24 @@ private static function fromXmlAndPaths(
 
         $composer_json = null;
         if (file_exists($composer_json_path)) {
-            if (!$composer_json = json_decode(file_get_contents($composer_json_path), true)) {
+            $composer_json = json_decode(file_get_contents($composer_json_path), true);
+            if (!is_array($composer_json)) {
                 throw new UnexpectedValueException('Invalid composer.json at ' . $composer_json_path);
             }
         }
-        foreach ($config->php_extensions as $ext => $_) {
-            $config->php_extensions[$ext] = isset($composer_json["require"]["ext-$ext"]);
+        $required_extensions = [];
+        foreach (($composer_json["require"] ?? []) as $required => $_) {
+            if (strpos($required, "ext-") === 0) {
+                $required_extensions[strtolower(substr($required, 4))] = true;
+            }
+        }
+        foreach ($required_extensions as $required_ext => $_) {
+            if (isset($config->php_extensions[$required_ext])) {
+                /** @psalm-suppress PropertyTypeCoercion isset doesn't narrow $required_ext like it should */
+                $config->php_extensions[$required_ext] = true;
+            } else {
+                $config->php_extensions_not_supported[$required_ext] = true;
+            }
         }
 
         if (isset($config_xml->enableExtensions) && isset($config_xml->enableExtensions->extension)) {
diff --git a/src/Psalm/Internal/Analyzer/ProjectAnalyzer.php b/src/Psalm/Internal/Analyzer/ProjectAnalyzer.php
index 8904b472c30..740735dc44a 100644
--- a/src/Psalm/Internal/Analyzer/ProjectAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/ProjectAnalyzer.php
@@ -59,6 +59,7 @@
 use function array_combine;
 use function array_diff;
 use function array_fill_keys;
+use function array_filter;
 use function array_keys;
 use function array_map;
 use function array_merge;
@@ -590,7 +591,9 @@ private function generatePHPVersionMessage(): string
                 break;
         }
 
-        return "Target PHP version: $version $source\n";
+        return "Target PHP version: $version $source Extensions enabled: "
+            . implode(", ", array_keys(array_filter($codebase->config->php_extensions))) . " (unsupported extensions: "
+            . implode(", ", array_keys($codebase->config->php_extensions_not_supported)) . ")\n";
     }
 
     public function check(string $base_dir, bool $is_diff = false): void
diff --git a/tests/EndToEnd/PsalmEndToEndTest.php b/tests/EndToEnd/PsalmEndToEndTest.php
index 59498a274df..e8e9ddb1ee5 100644
--- a/tests/EndToEnd/PsalmEndToEndTest.php
+++ b/tests/EndToEnd/PsalmEndToEndTest.php
@@ -20,6 +20,7 @@
 use function readdir;
 use function rmdir;
 use function str_replace;
+use function substr_count;
 use function sys_get_temp_dir;
 use function tempnam;
 use function unlink;
@@ -168,7 +169,7 @@ public function testPsalmDiff(): void
         $this->assertStringContainsString('InvalidReturnType', $result['STDOUT']);
         $this->assertStringContainsString('InvalidReturnStatement', $result['STDOUT']);
         $this->assertStringContainsString('3 errors', $result['STDOUT']);
-        $this->assertStringNotContainsString('E', $result['STDERR']);
+        $this->assertEquals(1, substr_count($result['STDERR'], 'E')); // Should only have 'E' from 'Extensions' in version message
 
         $this->assertSame(2, $result['CODE']);
 
diff --git a/tests/ProjectCheckerTest.php b/tests/ProjectCheckerTest.php
index 622e6948e04..36b0c6c0ae7 100644
--- a/tests/ProjectCheckerTest.php
+++ b/tests/ProjectCheckerTest.php
@@ -40,6 +40,13 @@ class ProjectCheckerTest extends TestCase
     /** @var ProjectAnalyzer */
     protected $project_analyzer;
 
+    private const EXPECTED_OUTPUT = "Target PHP version: 8.1 (set by tests) Extensions enabled: dom (unsupported "
+        . "extensions: simplexml, ctype, json, libxml, mbstring, tokenizer)\n"
+        . "Scanning files...\n"
+        . "Analyzing files...\n"
+        . "\n"
+    ;
+
     public static function setUpBeforeClass(): void
     {
         self::$config = new TestConfig();
@@ -97,13 +104,7 @@ public function testCheck(): void
         $this->project_analyzer->check('tests/fixtures/DummyProject');
         $output = ob_get_clean();
 
-        $this->assertSame(
-            'Target PHP version: 8.1 (set by tests)' . "\n"
-            . 'Scanning files...' . "\n"
-            . 'Analyzing files...' . "\n"
-            . "\n",
-            $output
-        );
+        $this->assertSame(self::EXPECTED_OUTPUT, $output);
 
         $this->assertSame(0, IssueBuffer::getErrorCount());
 
@@ -289,13 +290,7 @@ public function testCheckDir(): void
         $this->project_analyzer->checkDir('tests/fixtures/DummyProject');
         $output = ob_get_clean();
 
-        $this->assertSame(
-            'Target PHP version: 8.1 (set by tests)' . "\n"
-            . 'Scanning files...' . "\n"
-            . 'Analyzing files...' . "\n"
-            . "\n",
-            $output
-        );
+        $this->assertSame(self::EXPECTED_OUTPUT, $output);
 
         $this->assertSame(0, IssueBuffer::getErrorCount());
 
@@ -334,13 +329,7 @@ public function testCheckPaths(): void
         ]);
         $output = ob_get_clean();
 
-        $this->assertSame(
-            'Target PHP version: 8.1 (set by tests)' . "\n"
-            . 'Scanning files...' . "\n"
-            . 'Analyzing files...' . "\n"
-            . "\n",
-            $output
-        );
+        $this->assertSame(self::EXPECTED_OUTPUT, $output);
 
         $this->assertSame(0, IssueBuffer::getErrorCount());
 
@@ -379,13 +368,7 @@ public function testCheckFile(): void
         ]);
         $output = ob_get_clean();
 
-        $this->assertSame(
-            'Target PHP version: 8.1 (set by tests)' . "\n"
-            . 'Scanning files...' . "\n"
-            . 'Analyzing files...' . "\n"
-            . "\n",
-            $output
-        );
+        $this->assertSame(self::EXPECTED_OUTPUT, $output);
 
         $this->assertSame(0, IssueBuffer::getErrorCount());