diff --git a/CHANGELOG-v3.md b/CHANGELOG-v3.md
index 0f6a50863c1..ee81ffd26fb 100644
--- a/CHANGELOG-v3.md
+++ b/CHANGELOG-v3.md
@@ -12,6 +12,7 @@
 - Fixed a bug where the "Update all" button was missing on the updates page. ([#4938](https://github.com/craftcms/cms/issues/4938))
 - Fixed a bug where the “Updating search indexes” job could fail when updating search indexes for a Matrix block that contained a relational field.
 - Fixed a bug where it was impossible to query for entries using author id with the GraphQL API.
+- Fixed a bug where querying for Marix Blocks using the GraphQL API would not work.
 
 ## 3.3.3 - 2019-09-12
 
diff --git a/src/services/Gql.php b/src/services/Gql.php
index f7001804ab6..dacb1382360 100644
--- a/src/services/Gql.php
+++ b/src/services/Gql.php
@@ -170,6 +170,17 @@ public function getSchemaDef(GqlSchema $schema = null, $prebuildSchema = false):
                 'directives' => $this->_loadGqlDirectives(),
             ];
 
+            // For some reason, matrix types need to be explicitly defined, too,
+            // otherwise it will complain on querying matrix blocks
+            $typeGeneratorClass = MatrixBlockInterface::getTypeGenerator();
+
+            foreach ($typeGeneratorClass::generateTypes() as $type) {
+                $schemaConfig['types'][] = $type;
+            }
+
+            // TODO fire an event to allow modifying the $schemConfig.
+            // At least one use-case being adding workaround like for Matrix above.
+
             // If we're not required to pre-build the schema the relevant GraphQL types will be added to the Schema
             // as the query is being resolved thanks to the magic of lazy-loading, so we needn't worry.
             if (!$prebuildSchema) {