diff --git a/composer.json b/composer.json
index 0e758543a3..cb21a704c5 100644
--- a/composer.json
+++ b/composer.json
@@ -13,9 +13,9 @@
         "php": ">=7.2",
         "webonyx/graphql-php": "^0.13.4",
         "psr/container": "^1",
-        "doctrine/annotations": "^1.2",
+        "doctrine/annotations": "^1.7.0",
         "doctrine/cache": "^1.8",
-        "thecodingmachine/class-explorer": "^1.0.2",
+        "thecodingmachine/class-explorer": "^1.1.0",
         "psr/simple-cache": "^1",
         "phpdocumentor/reflection-docblock": "^4.3",
         "phpdocumentor/type-resolver": "^1.0.1",
diff --git a/src/Mappers/GlobTypeMapper.php b/src/Mappers/GlobTypeMapper.php
index effede5372..f9ee9d2411 100644
--- a/src/Mappers/GlobTypeMapper.php
+++ b/src/Mappers/GlobTypeMapper.php
@@ -64,11 +64,20 @@ protected function getClassList(): array
         if ($this->classes === null) {
             $this->classes = [];
             $explorer      = new GlobClassExplorer($this->namespace, $this->cache, $this->globTtl, $this->classNameMapper, $this->recursive);
-            $classes       = $explorer->getClasses();
-            foreach ($classes as $className) {
-                if (! class_exists($className) && ! interface_exists($className)) {
-                    continue;
+            $classes       = $explorer->getClassMap();
+            foreach ($classes as $className => $phpFile) {
+                if (! class_exists($className, false) && ! interface_exists($className, false)) {
+                    // Let's try to load the file if it was not imported yet.
+                    // We are importing the file manually to avoid triggering the autoloader.
+                    // The autoloader might trigger errors if the file does not respect PSR-4 or if the
+                    // Symfony DebugAutoLoader is installed. (see https://github.com/thecodingmachine/graphqlite/issues/216)
+                    require_once $phpFile;
+                    // Does it exists now?
+                    if (! class_exists($className, false) && ! interface_exists($className, false)) {
+                        continue;
+                    }
                 }
+
                 $refClass = new ReflectionClass($className);
                 $this->classes[$className] = $refClass;
             }
diff --git a/tests/Fixtures/Integration/Models/BadNamespaceClass.php b/tests/Fixtures/Integration/Models/BadNamespaceClass.php
new file mode 100644
index 0000000000..6ff471a75b
--- /dev/null
+++ b/tests/Fixtures/Integration/Models/BadNamespaceClass.php
@@ -0,0 +1,9 @@
+<?php
+
+/**
+ * This class has a bad namespace. It should not trigger errors when using GlobTypeMapper.
+ */
+class BadNamespaceClass
+{
+
+}