diff --git a/src/Psalm/Config.php b/src/Psalm/Config.php
index 908e85ce8..911ab332c 100644
--- a/src/Psalm/Config.php
+++ b/src/Psalm/Config.php
@@ -1111,7 +1111,8 @@ class Config
             $any_file_path_matched = false;
 
             foreach ($dependent_files as $dependent_file_path) {
-                if (($project_analyzer->full_run || $codebase->analyzer->canReportIssues($dependent_file_path))
+                if (($codebase->analyzer->canReportIssues($dependent_file_path)
+                        || $project_analyzer->canReportIssues($dependent_file_path))
                     && !$this->mustBeIgnored($dependent_file_path)
                 ) {
                     $any_file_path_matched = true;
diff --git a/src/Psalm/FileBasedPluginAdapter.php b/src/Psalm/FileBasedPluginAdapter.php
index b33b068e3..8cb67637d 100644
--- a/src/Psalm/FileBasedPluginAdapter.php
+++ b/src/Psalm/FileBasedPluginAdapter.php
@@ -18,6 +18,10 @@ class FileBasedPluginAdapter implements Plugin\PluginEntryPointInterface
 
     public function __construct(string $path, Config $config, Codebase $codebase)
     {
+        if (!$path) {
+            throw new \UnexpectedValueException('$path cannot be empty');
+        }
+
         $this->path = $path;
         $this->config = $config;
         $this->codebase = $codebase;
diff --git a/src/Psalm/Internal/Analyzer/ProjectAnalyzer.php b/src/Psalm/Internal/Analyzer/ProjectAnalyzer.php
index aa987ef82..ecdbadfb7 100644
--- a/src/Psalm/Internal/Analyzer/ProjectAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/ProjectAnalyzer.php
@@ -122,6 +122,11 @@ class ProjectAnalyzer
      */
     public $onchange_line_limit;
 
+    /**
+     * @var array<string,string>
+     */
+    private $project_files;
+
     const TYPE_COMPACT = 'compact';
     const TYPE_CONSOLE = 'console';
     const TYPE_PYLINT = 'pylint';
@@ -204,6 +209,26 @@ class ProjectAnalyzer
             }
         }
 
+        $project_files = [];
+
+        foreach ($this->config->getProjectDirectories() as $dir_name) {
+            $file_extensions = $this->config->getFileExtensions();
+
+            $file_paths = $this->file_provider->getFilesInDir($dir_name, $file_extensions);
+
+            foreach ($file_paths as $file_path) {
+                if ($this->config->isInProjectDirs($file_path)) {
+                    $project_files[$file_path] = $file_path;
+                }
+            }
+        }
+
+        foreach ($this->config->getProjectFiles() as $file_path) {
+            $project_files[$file_path] = $file_path;
+        }
+
+        $this->project_files = $project_files;
+
         $this->output_format = $output_format;
         self::$instance = $this;
     }
@@ -323,6 +348,16 @@ class ProjectAnalyzer
         return self::$instance;
     }
 
+    /**
+     * @param  string $file_path
+     *
+     * @return bool
+     */
+    public function canReportIssues($file_path)
+    {
+        return isset($this->project_files[$file_path]);
+    }
+
     /**
      * @param  string  $base_dir
      * @param  bool $is_diff
@@ -361,36 +396,18 @@ class ProjectAnalyzer
             echo 'Scanning files...' . "\n";
         }
 
-        $all_files_to_scan = [];
-
-        foreach ($this->config->getProjectDirectories() as $dir_name) {
-            $file_extensions = $this->config->getFileExtensions();
-
-            $file_paths = $this->file_provider->getFilesInDir($dir_name, $file_extensions);
-
-            foreach ($file_paths as $file_path) {
-                if ($this->config->isInProjectDirs($file_path)) {
-                    $all_files_to_scan[$file_path] = $file_path;
-                }
-            }
-        }
-
-        foreach ($this->config->getProjectFiles() as $file_path) {
-            $all_files_to_scan[$file_path] = $file_path;
-        }
-
         if ($diff_files === null
             || $deleted_files === null
             || count($diff_files) > 200
             || $this->codebase->find_unused_code) {
-            $this->codebase->scanner->addFilesToDeepScan($all_files_to_scan);
+            $this->codebase->scanner->addFilesToDeepScan($this->project_files);
         }
 
         if ($diff_files === null
             || $deleted_files === null
             || count($diff_files) > 200
         ) {
-            $this->codebase->analyzer->addFiles($all_files_to_scan);
+            $this->codebase->analyzer->addFiles($this->project_files);
 
             $this->config->initializePlugins($this);
 
diff --git a/tests/TestConfig.php b/tests/TestConfig.php
index d3e7e29e8..74e430d91 100644
--- a/tests/TestConfig.php
+++ b/tests/TestConfig.php
@@ -19,8 +19,19 @@ class TestConfig extends Config
 
         $this->base_dir = getcwd() . DIRECTORY_SEPARATOR;
 
-        $this->project_files = new Config\ProjectFileFilter(true);
-        $this->project_files->addDirectory($this->base_dir . 'src');
+        $this->project_files = Config\ProjectFileFilter::loadFromXMLElement(
+            new \SimpleXMLElement(
+                '<?xml version="1.0"?>
+                <projectFiles>
+                    <directory name="src" />
+                    <ignoreFiles>
+                        <directory name="src/Psalm/Internal/Stubs" />
+                    </ignoreFiles>
+                </projectFiles>'
+            ),
+            $this->base_dir,
+            true
+        );
 
         $this->collectPredefinedConstants();
         $this->collectPredefinedFunctions();