diff --git a/src/ComposerRequireChecker/ASTLocator/FileAST.php b/src/ComposerRequireChecker/ASTLocator/FileAST.php
new file mode 100644
index 00000000..20ff3c1e
--- /dev/null
+++ b/src/ComposerRequireChecker/ASTLocator/FileAST.php
@@ -0,0 +1,45 @@
+<?php
+
+namespace ComposerRequireChecker\ASTLocator;
+
+use Traversable;
+
+class FileAST
+{
+    /**
+     * @var string
+     */
+    private $file;
+
+    /**
+     * @var Traversable
+     */
+    private $ast;
+
+    /**
+     * @param string $file
+     * @param Traversable|array|null $ast
+     *
+     */
+    public function __construct(string $file, $ast)
+    {
+        $this->file = $file;
+        $this->ast = $ast;
+    }
+
+    /**
+     * @return string
+     */
+    public function getFile()
+    {
+        return $this->file;
+    }
+
+    /**
+     * @return Traversable|array
+     */
+    public function getAst()
+    {
+        return $this->ast;
+    }
+}
diff --git a/src/ComposerRequireChecker/ASTLocator/LocateASTFromFiles.php b/src/ComposerRequireChecker/ASTLocator/LocateASTFromFiles.php
index 7eebc726..1ca45b30 100644
--- a/src/ComposerRequireChecker/ASTLocator/LocateASTFromFiles.php
+++ b/src/ComposerRequireChecker/ASTLocator/LocateASTFromFiles.php
@@ -27,12 +27,12 @@ public function __construct(Parser $parser, ?ErrorHandler $errorHandler)
     /**
      * @param Traversable|string[] $files
      *
-     * @return Traversable|array[] a series of AST roots, one for each given file
+     * @return Traversable|FileAST[] a series of AST roots, one for each given file
      */
     public function __invoke(Traversable $files): Traversable
     {
         foreach ($files as $file) {
-            yield $this->parser->parse(file_get_contents($file), $this->errorHandler);
+            yield new FileAST($file, $this->parser->parse(file_get_contents($file), $this->errorHandler));
         }
     }
 }
diff --git a/src/ComposerRequireChecker/Cli/CheckCommand.php b/src/ComposerRequireChecker/Cli/CheckCommand.php
index 3cc4255f..94edfc05 100644
--- a/src/ComposerRequireChecker/Cli/CheckCommand.php
+++ b/src/ComposerRequireChecker/Cli/CheckCommand.php
@@ -67,12 +67,16 @@ protected function execute(InputInterface $input, OutputInterface $output): int
 
         $sourcesASTs = $this->getASTFromFilesLocator($input);
 
-        $definedVendorSymbols = (new LocateDefinedSymbolsFromASTRoots())->__invoke($sourcesASTs(
+        list($definedVendorSymbols, $additionalFiles) = (new LocateDefinedSymbolsFromASTRoots())->__invoke($sourcesASTs(
             (new ComposeGenerators())->__invoke(
                 $getPackageSourceFiles($composerJson),
                 (new LocateComposerPackageDirectDependenciesSourceFiles())->__invoke($composerJson)
             )
         ));
+        while ($additionalFiles && count($additionalFiles)) {
+            list($vendorSymbols, $additionalFiles) = (new LocateDefinedSymbolsFromASTRoots())->__invoke($sourcesASTs($additionalFiles));
+            $definedVendorSymbols = array_unique(array_merge($vendorSymbols, $definedVendorSymbols));
+        }
 
         $definedExtensionSymbols = (new LocateDefinedSymbolsFromExtensions())->__invoke(
             (new DefinedExtensionsResolver())->__invoke($composerJson, $options->getPhpCoreExtensions())
diff --git a/src/ComposerRequireChecker/DefinedSymbolsLocator/LocateDefinedSymbolsFromASTRoots.php b/src/ComposerRequireChecker/DefinedSymbolsLocator/LocateDefinedSymbolsFromASTRoots.php
index 1e5fef11..561d02ff 100644
--- a/src/ComposerRequireChecker/DefinedSymbolsLocator/LocateDefinedSymbolsFromASTRoots.php
+++ b/src/ComposerRequireChecker/DefinedSymbolsLocator/LocateDefinedSymbolsFromASTRoots.php
@@ -2,7 +2,9 @@
 
 namespace ComposerRequireChecker\DefinedSymbolsLocator;
 
+use ArrayIterator;
 use ComposerRequireChecker\NodeVisitor\DefinedSymbolCollector;
+use ComposerRequireChecker\NodeVisitor\IncludeCollector;
 use PhpParser\NodeTraverser;
 use PhpParser\NodeVisitor\NameResolver;
 use Traversable;
@@ -21,15 +23,17 @@ public function __invoke(Traversable $ASTs): array
 
         $traverser->addVisitor(new NameResolver());
         $traverser->addVisitor($collector = new DefinedSymbolCollector());
+        $traverser->addVisitor($includes = new IncludeCollector());
 
         $astSymbols = [];
+        $additionalFiles = [];
 
         foreach ($ASTs as $astRoot) {
-            $traverser->traverse($astRoot);
-
+            $traverser->traverse($astRoot->getAst());
             $astSymbols[] = $collector->getDefinedSymbols();
+            $additionalFiles = array_merge($additionalFiles, $includes->getIncluded($astRoot->getFile()));
         }
 
-        return array_values(array_unique(array_merge([], ...$astSymbols)));
+        return [array_values(array_unique(array_merge([], ...$astSymbols))), new ArrayIterator($additionalFiles)];
     }
 }
diff --git a/src/ComposerRequireChecker/NodeVisitor/IncludeCollector.php b/src/ComposerRequireChecker/NodeVisitor/IncludeCollector.php
new file mode 100644
index 00000000..b039150a
--- /dev/null
+++ b/src/ComposerRequireChecker/NodeVisitor/IncludeCollector.php
@@ -0,0 +1,129 @@
+<?php
+
+namespace ComposerRequireChecker\NodeVisitor;
+
+use FilesystemIterator;
+use InvalidArgumentException;
+use PhpParser\Node;
+use PhpParser\Node\Expr;
+use PhpParser\Node\Expr\BinaryOp\Concat;
+use PhpParser\Node\Expr\ConstFetch;
+use PhpParser\Node\Expr\Include_;
+use PhpParser\Node\Expr\Variable;
+use PhpParser\Node\Scalar\MagicConst\Dir;
+use PhpParser\Node\Scalar\MagicConst\File;
+use PhpParser\Node\Scalar\String_;
+use PhpParser\NodeVisitorAbstract;
+use RecursiveDirectoryIterator;
+use RecursiveIteratorIterator;
+
+final class IncludeCollector extends NodeVisitorAbstract
+{
+    /**
+     * @var Expr[]
+     */
+    private $included = [];
+
+    /**
+     * {@inheritDoc}
+     */
+    public function beforeTraverse(array $nodes)
+    {
+        $this->included = [];
+        return parent::beforeTraverse($nodes);
+    }
+
+    /**
+     * @param string $file
+     * @return string[]
+     */
+    public function getIncluded(string $file): array
+    {
+        $included = [];
+        foreach ($this->included as $exp) {
+            try {
+                $this->computePath($included, $this->processIncludePath($exp, $file), $file);
+            } catch(InvalidArgumentException $x) {
+                var_dump($x->getMessage());
+            }
+        }
+        return $included;
+    }
+
+    /**
+     * @param array $included
+     * @param string $path
+     * @param string $self
+     * @return void
+     */
+    private function computePath(array &$included, string $path, string $self)
+    {
+        if (!preg_match('#^([A-Z]:)?/#i', str_replace('\\', '/', $path))) {
+            $path = dirname($self).'/'.$path;
+        }
+        if (false === strpos($path, '{var}')) {
+            $included[] = $path;
+            return;
+        }
+        $parts = explode('{var}', $path);
+        $regex = [];
+        foreach($parts as $part) {
+            $regex[] = preg_quote(str_replace('\\', '/', $part), '/');
+        }
+        $regex = '/^'.implode('.+', $regex).'$/';
+        $self = str_replace('\\', '/', $self);
+        foreach (new RecursiveIteratorIterator(
+            new RecursiveDirectoryIterator(
+                $parts[0],
+                FilesystemIterator::CURRENT_AS_PATHNAME | FilesystemIterator::SKIP_DOTS
+            )
+        ) as $file) {
+            $rfile = str_replace('\\', '/', $file);
+            if ($rfile !== $self && preg_match('/\\.php$/i', $rfile) && preg_match($regex, $rfile)) {
+                $included[] = $file;
+            }
+        }
+    }
+
+    /**
+     * @param string|Exp $exp
+     * @param string $file
+     * @return string
+     * @throws InvalidArgumentException
+     */
+    private function processIncludePath($exp, string $file): string
+    {
+        if (is_string($exp)) {
+            return $exp;
+        }
+        if ($exp instanceof Concat) {
+            return $this->processIncludePath($exp->left, $file).$this->processIncludePath($exp->right, $file);
+        }
+        if ($exp instanceof Dir) {
+            return dirname($file);
+        }
+        if ($exp instanceof File) {
+            return $file;
+        }
+        if ($exp instanceof ConstFetch && $exp->name === 'DIRECTORY_SEPARATOR') {
+            return DIRECTORY_SEPARATOR;
+        }
+        if ($exp instanceof String_) {
+            return $exp->value;
+        }
+        if ($exp instanceof Variable || $exp instanceof ConstFetch) {
+            return '{var}';
+        }
+        throw new InvalidArgumentException('can\'t yet handle '.$exp->getType());
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function enterNode(Node $node)
+    {
+        if ($node instanceof Include_) {
+            $this->included[] = $node->expr;
+        }
+    }
+}
diff --git a/src/ComposerRequireChecker/UsedSymbolsLocator/LocateUsedSymbolsFromASTRoots.php b/src/ComposerRequireChecker/UsedSymbolsLocator/LocateUsedSymbolsFromASTRoots.php
index 5d72bd88..315c0685 100644
--- a/src/ComposerRequireChecker/UsedSymbolsLocator/LocateUsedSymbolsFromASTRoots.php
+++ b/src/ComposerRequireChecker/UsedSymbolsLocator/LocateUsedSymbolsFromASTRoots.php
@@ -25,7 +25,7 @@ public function __invoke(Traversable $ASTs): array
         $astSymbols = [];
 
         foreach ($ASTs as $astRoot) {
-            $traverser->traverse($astRoot);
+            $traverser->traverse($astRoot->getAst());
 
             $astSymbols[] = $collector->getCollectedSymbols();
         }