diff --git a/composer.json b/composer.json
index 790bfd1..9a81a05 100644
--- a/composer.json
+++ b/composer.json
@@ -5,9 +5,7 @@
   "type": "phpstan-extension",
   "require": {
     "php": "^7.4 || ^8.0",
-    "phpstan/phpstan": "^1.8",
-    "symfony/polyfill-php80": "^v1.27.0",
-    "symfony/yaml": "^5.4 || ^6.0"
+    "phpstan/phpstan": "^1.8"
   },
   "require-dev": {
     "phpstan/phpstan-phpunit": "^1.2",
diff --git a/src/ModuliteYaml/ModuliteData.php b/src/ModuliteYaml/ModuliteData.php
index f4997c1..b99c6b9 100644
--- a/src/ModuliteYaml/ModuliteData.php
+++ b/src/ModuliteYaml/ModuliteData.php
@@ -373,11 +373,11 @@ static function create_from_composer_json(ComposerJsonData $composer_json, bool
     if ($has_modulite_yaml_also) {
       $yaml_filename = dirname($composer_json->json_filename) . '/.modulite.yaml';
       try {
-        $y_file = \Symfony\Component\Yaml\Yaml::parseFile($yaml_filename);
+        $y_file = YamlParserNoSymfony::parseFromFile($yaml_filename);
         $parser = new ModuliteYamlParser($out);
-        $parser->parse_modulite_yaml_file(is_array($y_file) ? $y_file : []);
-      } catch (\Symfony\Component\Yaml\Exception\ParseException $ex) {
-        $out->fire_yaml_error($ex->getMessage(), $ex->getParsedLine());
+        $parser->parse_modulite_yaml_file($y_file);
+      } catch (YamlParserNoSymfonyException $ex) {
+        $out->fire_yaml_error($ex->getMessage(), $ex->getLine());
       }
     }
 
@@ -393,11 +393,11 @@ static function create_from_modulite_yaml(string $yaml_filename, ?ModuliteData $
     $out->is_composer_package = false;
 
     try {
-      $y_file = \Symfony\Component\Yaml\Yaml::parseFile($out->yaml_filename);
+      $y_file = YamlParserNoSymfony::parseFromFile($out->yaml_filename);
       $parser = new ModuliteYamlParser($out);
-      $parser->parse_modulite_yaml_file(is_array($y_file) ? $y_file : []);
-    } catch (\Symfony\Component\Yaml\Exception\ParseException $ex) {
-      $out->fire_yaml_error($ex->getMessage(), $ex->getParsedLine());
+      $parser->parse_modulite_yaml_file($y_file);
+    } catch (YamlParserNoSymfonyException $ex) {
+      $out->fire_yaml_error($ex->getMessage(), $ex->getLine());
     }
 
     return $out;
diff --git a/src/ModuliteYaml/YamlParserNoSymfony.php b/src/ModuliteYaml/YamlParserNoSymfony.php
new file mode 100644
index 0000000..dadaa77
--- /dev/null
+++ b/src/ModuliteYaml/YamlParserNoSymfony.php
@@ -0,0 +1,179 @@
+<?php
+
+namespace ModulitePHPStan\ModuliteYaml;
+
+/**
+ * The purpose of this class is to avoid "symfony/yaml" dependency.
+ * It successfully parses a limited subset of .yaml files,
+ * which is quite enough for .modulite.yaml
+ * (no links, strings are quoted, only two levels of depth)
+ */
+class YamlParserNoSymfony {
+  static public function parseFromString(string $yaml): array {
+    return self::parseYamlContents(preg_split('/\n/', $yaml), 'user-string');
+  }
+
+  static public function parseFromFile(string $file_name): array {
+    return self::parseYamlContents(file($file_name), $file_name);
+  }
+
+  static private function parseYamlContents(array $lines, string $file_name): array {
+    /** @var mixed[] $out */
+    $out = [];
+
+    $last_key = null;
+    $last_key_nested = null;
+
+    $assignValueAtCurrentKey = function(?string $value) use (&$last_key, &$last_key_nested, &$out) {
+      if ($last_key_nested !== null) {
+        $out[$last_key][$last_key_nested] = $value;
+      } else if ($last_key !== null) {
+        $out[$last_key] = $value;
+      }
+    };
+
+    $pushValueAtCurrentKey = function(string $value) use (&$last_key, &$last_key_nested, &$out) {
+      if ($last_key_nested !== null) {
+        $out[$last_key][$last_key_nested][] = $value;
+      } else if ($last_key !== null) {
+        $out[$last_key][] = $value;
+      }
+    };
+
+    foreach ($lines as $i => $line) {
+      $line = rtrim($line);
+      $offset = 0;
+      self::skipSpaces($line, $offset);
+      $n_spaces = $offset;
+
+      if ($offset >= strlen($line)) {
+        continue;
+      }
+
+      if ($line[$offset] === '#') {
+        continue;
+      }
+
+      if ($line[$offset] === '-') {
+        if ($last_key === null || is_string($out[$last_key])) {
+          throw new YamlParserNoSymfonyException($file_name, "list in a strange place", $i + 1);
+        }
+        $offset++;
+        $value = self::parseString($line, $offset);
+        if ($value === null) {
+          throw new YamlParserNoSymfonyException($file_name, "expected a string", $i + 1);
+        }
+        $pushValueAtCurrentKey($value);
+        continue;
+      }
+
+      $nameBeforeColon = self::parseNameBeforeColon($line, $offset);
+      if ($nameBeforeColon === null) {
+        throw new YamlParserNoSymfonyException($file_name, "expected ':'", $i + 1);
+      }
+
+      if ($n_spaces > 0) {  // support only 2 depth levels
+        $last_key_nested = $nameBeforeColon;
+      } else {
+        $last_key = $nameBeforeColon;
+        $last_key_nested = null;
+      }
+
+      self::skipSpaces($line, $offset);
+      if ($offset < strlen($line) && $line[$offset] !== '#') {
+        $value = self::parseString($line, $offset);
+        if ($value === null) {
+          throw new YamlParserNoSymfonyException($file_name, "expected a string", $i + 1);
+        }
+        $assignValueAtCurrentKey($value);
+      } else {
+        $assignValueAtCurrentKey(null);
+      }
+    }
+
+    return $out;
+  }
+
+  static private function parseString(string $line, int &$offset): ?string {
+    self::skipSpaces($line, $offset);
+    if ($offset >= strlen($line)) {
+      return null;
+    }
+
+    return $line[$offset] === '"'
+      ? self::parseQuotedString($line, $offset)
+      : self::parseNonQuotedString($line, $offset);
+  }
+
+  static private function skipSpaces(string $line, int &$offset) {
+    while ($offset < strlen($line) && $line[$offset] === ' ') {
+      $offset++;
+    }
+  }
+
+  static private function parseNameBeforeColon(string $line, int &$offset): ?string {
+    $name = '';
+
+    if ($line[$offset] === '"' || $line[$offset] === "'") {
+      $name = self::parseQuotedString($line, $offset);
+      if ($name === null || $offset >= strlen($line) || $line[$offset] !== ':') {
+        return null;
+      }
+    } else {
+      $pos = strpos($line, ':', $offset);
+      if ($pos === false) {
+        return null;
+      }
+      $name = substr($line, $offset, $pos - $offset);
+      $offset = $pos;
+    }
+
+    $offset = $offset + 1;
+    return $name;
+  }
+
+  static private function parseNonQuotedString(string $line, int &$offset): ?string {
+    $value = '';
+
+    for ($i = $offset; $i < strlen($line); ++$i) {
+      switch ($line[$i]) {
+        case '#':
+          break 2;
+        default:
+          $value .= $line[$i];
+      }
+    }
+
+    while ($i > $offset && $line[$i - 1] === ' ') {
+      $i--;
+      $value = substr($value, 0, -1);
+    }
+
+    $offset = $i;
+    return $value;
+  }
+
+  static private function parseQuotedString(string $line, int &$offset): ?string {
+    $quote = $line[$offset];  // " or '
+    $value = '';
+
+    for ($i = $offset + 1; $i < strlen($line); ++$i) {
+      switch ($line[$i]) {
+        case '\\':
+          $value .= $line[++$i];
+          break;
+        case $quote:
+          break 2;
+        default:
+          $value .= $line[$i];
+      }
+    }
+
+    if ($i == strlen($line) || $line[$i] !== $quote) {
+      return null;
+    }
+
+    $offset = $i + 1;
+    return $value;
+  }
+}
diff --git a/src/ModuliteYaml/YamlParserNoSymfonyException.php b/src/ModuliteYaml/YamlParserNoSymfonyException.php
new file mode 100644
index 0000000..5e431be
--- /dev/null
+++ b/src/ModuliteYaml/YamlParserNoSymfonyException.php
@@ -0,0 +1,11 @@
+<?php
+
+namespace ModulitePHPStan\ModuliteYaml;
+
+class YamlParserNoSymfonyException extends \RuntimeException {
+  public function __construct(string $file_name, string $message, int $line_number) {
+    parent::__construct($message);
+    $this->file = $file_name;
+    $this->line = $line_number;
+  }
+}
diff --git a/tests/YamlParserNoSymfonyTestCase.php b/tests/YamlParserNoSymfonyTestCase.php
new file mode 100644
index 0000000..d0fdc07
--- /dev/null
+++ b/tests/YamlParserNoSymfonyTestCase.php
@@ -0,0 +1,109 @@
+<?php
+
+namespace ModuliteTests;
+
+use ModulitePHPStan\ModuliteYaml\YamlParserNoSymfony;
+use ModulitePHPStan\ModuliteYaml\YamlParserNoSymfonyException;
+
+class YamlParserNoSymfonyTestCase extends \PHPUnit\Framework\TestCase {
+  function testSuccess() {
+    $yaml = <<<'YAML'
+name: "@utils"
+namespace: "Algo101\\"
+hello1: hello1
+hello2: hello2 # comment
+hello3: "hello3"
+hello4: "hello4" # comment
+"hello5": hello5
+"hello 6": "hello 6"
+"hello:7": "hello:7"
+"hello'\"8": "hello'\"8" # comment
+hello9:
+hello10:            # comment
+
+export:
+  "asdf":
+    - ""
+  nested:
+    - one
+    - Export\ Class           
+    - Export\ Class             # comment
+    - "Export\\ Class         " # comment
+    - "Export\\Class::method()" # comment    
+
+require: "asdf"
+
+map:
+  k1: v1
+  k2: 
+  - v2
+  k3: v3
+
+allow-internal-access:
+  - "Algo101"
+YAML;
+    $expected = [
+      'name'                  => '@utils',
+      'namespace'             => 'Algo101\\',
+      'hello1'                => 'hello1',
+      'hello2'                => 'hello2',
+      'hello3'                => 'hello3',
+      'hello4'                => 'hello4',
+      'hello5'                => 'hello5',
+      'hello 6'               => 'hello 6',
+      'hello:7'               => 'hello:7',
+      'hello\'"8'             => 'hello\'"8',
+      'hello9'                => null,
+      'hello10'               => null,
+      'export'                => [
+        'asdf'   => [''],
+        'nested' => [
+          'one',
+          "Export\\ Class",
+          "Export\\ Class",
+          "Export\\ Class         ",
+          "Export\\Class::method()"
+        ]
+      ],
+      'require'               => 'asdf',
+      'map' => [
+        'k1' => 'v1',
+        'k2' => ['v2'],
+        'k3' => 'v3',
+      ],
+      'allow-internal-access' => ['Algo101'],
+    ];
+
+    $actual = YamlParserNoSymfony::parseFromString($yaml);
+    $this->assertSame($expected, $actual);
+  }
+
+  function testError1() {
+    $yaml = <<<'YAML'
+name: "asdf"
+- asdf
+YAML;
+    $this->expectException(YamlParserNoSymfonyException::class);
+    $this->expectExceptionMessage("list in a strange place");
+    YamlParserNoSymfony::parseFromString($yaml);
+  }
+
+  function testError2() {
+    $yaml = <<<'YAML'
+"asdf"
+YAML;
+    $this->expectException(YamlParserNoSymfonyException::class);
+    $this->expectExceptionMessage("expected ':'");
+    YamlParserNoSymfony::parseFromString($yaml);
+  }
+
+  function testError3() {
+    $yaml = <<<'YAML'
+exports:
+-
+YAML;
+    $this->expectException(YamlParserNoSymfonyException::class);
+    $this->expectExceptionMessage("expected a string");
+    YamlParserNoSymfony::parseFromString($yaml);
+  }
+}
diff --git a/tests/php/005_inheritance/005_inheritance.php b/tests/php/005_inheritance/005_inheritance.php
index 72c1bae..0998e26 100644
--- a/tests/php/005_inheritance/005_inheritance.php
+++ b/tests/php/005_inheritance/005_inheritance.php
@@ -8,6 +8,7 @@
 use Feed005\Rank005\RankImpl1;
 use Feed005\Rank005\RankImpl2;
 use Feed005\SenderFactory;
+require_once 'plain005/plain005.php';
 
 GImportTrait::pubStaticFn();
 $mmm = new GImportTrait;
@@ -32,6 +33,7 @@ function printCurDescInherit() {
 callSend(SenderFactory::createSender('sms'));
 
 printCurDescInherit();
+plainPrintCurDescInherit();
 
 Common005\CallOthers005::accessGloDer();
 Common005\CallOthers005::accessMessage();
diff --git a/tests/php/005_inheritance/ConnectNoMod005/ErrNoMod005.php b/tests/php/005_inheritance/ConnectNoMod005/ErrNoMod005.php
new file mode 100644
index 0000000..0ca8653
--- /dev/null
+++ b/tests/php/005_inheritance/ConnectNoMod005/ErrNoMod005.php
@@ -0,0 +1,6 @@
+<?php
+
+namespace ConnectNoMod005;
+
+final class ErrNoMod005 extends \SakCommon005\ErrSak005 {
+}
diff --git a/tests/php/005_inheritance/SakCommon005/.modulite.yaml b/tests/php/005_inheritance/SakCommon005/.modulite.yaml
new file mode 100644
index 0000000..f37fa63
--- /dev/null
+++ b/tests/php/005_inheritance/SakCommon005/.modulite.yaml
@@ -0,0 +1,12 @@
+name: "@sak"
+namespace: "SakCommon005\\"
+
+export:
+  - "ErrSak005"
+
+force-internal:
+
+require:
+  - "@feed"
+
+allow-internal-access:
diff --git a/tests/php/005_inheritance/SakCommon005/ErrSak005.php b/tests/php/005_inheritance/SakCommon005/ErrSak005.php
new file mode 100644
index 0000000..41f9348
--- /dev/null
+++ b/tests/php/005_inheritance/SakCommon005/ErrSak005.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace SakCommon005;
+
+class ErrSak005 {
+    const MODE = 1;
+    static public int $count = 0;
+
+    static function create() {
+        echo "create err";
+        return new static;
+    }
+}
diff --git a/tests/php/005_inheritance/plain005/.modulite.yaml b/tests/php/005_inheritance/plain005/.modulite.yaml
new file mode 100644
index 0000000..c1c54e0
--- /dev/null
+++ b/tests/php/005_inheritance/plain005/.modulite.yaml
@@ -0,0 +1,14 @@
+name: "@plain005"
+namespace: ""
+
+export:
+  - "plainPrintCurDescInherit()"
+
+force-internal:
+
+require:
+  - "ConnectNoMod005\\ErrNoMod005::MODE"
+  - "ConnectNoMod005\\ErrNoMod005::$count"
+  - "ConnectNoMod005\\ErrNoMod005::create()"
+
+allow-internal-access:
diff --git a/tests/php/005_inheritance/plain005/plain005.php b/tests/php/005_inheritance/plain005/plain005.php
new file mode 100644
index 0000000..120153e
--- /dev/null
+++ b/tests/php/005_inheritance/plain005/plain005.php
@@ -0,0 +1,7 @@
+<?php
+
+function plainPrintCurDescInherit() {
+    ConnectNoMod005\ErrNoMod005::create();
+    ConnectNoMod005\ErrNoMod005::MODE;
+    ConnectNoMod005\ErrNoMod005::$count++;
+}