diff --git a/src/Search/Query/Compound/FunctionScoreQuery.php b/src/Search/Query/Compound/FunctionScoreQuery.php
index a4d4663..5699197 100644
--- a/src/Search/Query/Compound/FunctionScoreQuery.php
+++ b/src/Search/Query/Compound/FunctionScoreQuery.php
@@ -59,7 +59,7 @@ public function toArray()
             if (!empty($queryArray)) {
                 $array['query'] = $queryArray;
             } else {
-                $array['query'] = ['match_all' => []];
+                $array['query'] = ['match_all' => new \stdClass()];
             }
         }
 
diff --git a/tests/Search/Query/Compound/FunctionScoreQueryTest.php b/tests/Search/Query/Compound/FunctionScoreQueryTest.php
index 96e5f82..9baf962 100644
--- a/tests/Search/Query/Compound/FunctionScoreQueryTest.php
+++ b/tests/Search/Query/Compound/FunctionScoreQueryTest.php
@@ -59,11 +59,11 @@ public function testToArray()
                         ]
                     ]
                 ],
-                'weight'     => 34.12,
-                'boost'      => 5.1,
-                'max_boost'  => 14.3,
+                'weight' => 34.12,
+                'boost' => 5.1,
+                'max_boost' => 14.3,
                 'boost_mode' => 'multiply',
-                'min_score'  => 1,
+                'min_score' => 1,
             ]
         ];
 
@@ -99,4 +99,21 @@ public function testToArrayMinimumFields()
 
         $this->assertEquals($expectedArray, $functionScoreQuery->toArray());
     }
+
+    public function testEmptyQuery()
+    {
+        $functionScoreQuery = new FunctionScoreQuery();
+
+        $functionScoreQuery->setQuery(new BoolQuery());
+
+        $expectedArray = [
+            'function_score' => [
+                'query' => [
+                    'match_all' => new \stdClass()
+                ],
+            ],
+        ];
+
+        $this->assertEquals($expectedArray, $functionScoreQuery->toArray());
+    }
 }