diff --git a/lib/jekyll/filters.rb b/lib/jekyll/filters.rb
index 65fc7e41..3c5d125d 100644
--- a/lib/jekyll/filters.rb
+++ b/lib/jekyll/filters.rb
@@ -13,7 +13,7 @@ module Jekyll
     def markdownify(input)
       site = @context.registers[:site]
       converter = site.find_converter_instance(Jekyll::Converters::Markdown)
-      converter.convert(input)
+      converter.convert(input.to_s)
     end
 
     # Convert quotes into smart quotes.
@@ -24,7 +24,7 @@ module Jekyll
     def smartify(input)
       site = @context.registers[:site]
       converter = site.find_converter_instance(Jekyll::Converters::SmartyPants)
-      converter.convert(input)
+      converter.convert(input.to_s)
     end
 
     # Convert a Sass string into CSS output.
diff --git a/test/test_filters.rb b/test/test_filters.rb
index a2184c37..66c7c551 100644
--- a/test/test_filters.rb
+++ b/test/test_filters.rb
@@ -40,6 +40,13 @@ class TestFilters < JekyllUnitTest
       )
     end
 
+    should "markdownify with a number" do
+      assert_equal(
+        "<p>404</p>\n",
+        @filter.markdownify(404)
+      )
+    end
+
     context "smartify filter" do
       should "convert quotes and typographic characters" do
         assert_equal(
@@ -81,6 +88,13 @@ class TestFilters < JekyllUnitTest
         assert_equal "5 &gt; 4", @filter.smartify("5 > 4")
         assert_equal "This &amp; that", @filter.smartify("This & that")
       end
+
+      should "convert a number to a string" do
+        assert_equal(
+          "404",
+          @filter.smartify(404)
+        )
+      end
     end
 
     should "sassify with simple string" do