diff --git a/lib/searchkick/query.rb b/lib/searchkick/query.rb
index 36b0f31..7f8ac66 100644
--- a/lib/searchkick/query.rb
+++ b/lib/searchkick/query.rb
@@ -872,8 +872,12 @@ module Searchkick
           }
         }
 
-        if value[:missing].present? && !below50?
-          script_score[:field_value_factor].merge!({missing: value[:missing].to_f})
+        if value[:missing].present?
+          if below50?
+            raise ArgumentError, "Option 'missing' for boost_by supported in Elasticsearch 5 or greater"
+          else
+            script_score[:field_value_factor].merge!({missing: value[:missing].to_f})
+          end
         end
 
         {
diff --git a/test/boost_test.rb b/test/boost_test.rb
index 75e5e7c..de79720 100644
--- a/test/boost_test.rb
+++ b/test/boost_test.rb
@@ -117,8 +117,6 @@ class BoostTest < Minitest::Test
   end
 
   def test_boost_by_missing_field
-    skip if elasticsearch_below50?
-
     store [
       {name: "Tomato A"},
       {name: "Tomato B", orders_count: 10},
@@ -129,7 +127,13 @@ class BoostTest < Minitest::Test
       assert_order "tomato", ["Tomato C", "Tomato B", "Tomato A"], boost_by: {orders_count: {factor: 5}, orders_value: {factor: 5}}
     end
 
-    assert_order "tomato", ["Tomato C", "Tomato B", "Tomato A"], boost_by: {orders_count: {factor: 5}, orders_value: {factor: 5, missing: 1}}
+    if elasticsearch_below50?
+      assert_raises(ArgumentError) do
+        assert_order "tomato", ["Tomato C", "Tomato B", "Tomato A"], boost_by: {orders_count: {factor: 5}, orders_value: {factor: 5, missing: 1}}
+      end
+    else
+      assert_order "tomato", ["Tomato C", "Tomato B", "Tomato A"], boost_by: {orders_count: {factor: 5}, orders_value: {factor: 5, missing: 1}}
+    end
   end
 
   def test_boost_by_boost_mode_multiply
--
libgit2 0.21.0