diff --git a/src/Psalm/Config.php b/src/Psalm/Config.php
index c26ed6421..3c59748b4 100644
--- a/src/Psalm/Config.php
+++ b/src/Psalm/Config.php
@@ -1876,6 +1876,10 @@ class Config
         }
 
         if ($this->autoloader) {
+            // somee classes that we think are missing may not actually be missing
+            // as they might be autoloadable once we require the autoloader below
+            $codebase->classlikes->forgetMissingClassLikes();
+
             // do this in a separate method so scope does not leak
             $this->requireAutoloader($this->autoloader);
 
diff --git a/src/Psalm/Internal/Codebase/ClassLikes.php b/src/Psalm/Internal/Codebase/ClassLikes.php
index ee84e3066..4d38839bb 100644
--- a/src/Psalm/Internal/Codebase/ClassLikes.php
+++ b/src/Psalm/Internal/Codebase/ClassLikes.php
@@ -2315,6 +2315,11 @@ class ClassLikes
             && $this->existing_classlikes_lc[$fq_classlike_name_lc];
     }
 
+    public function forgetMissingClassLikes() : void
+    {
+        $this->existing_classlikes_lc = \array_filter($this->existing_classlikes_lc);
+    }
+
     /**
      * @param string $fq_class_name
      *