diff --git a/app/logical/sources/strategies/tumblr.rb b/app/logical/sources/strategies/tumblr.rb
index 49f519c43..411a9a9e3 100644
--- a/app/logical/sources/strategies/tumblr.rb
+++ b/app/logical/sources/strategies/tumblr.rb
@@ -1,12 +1,13 @@
 module Sources::Strategies
   class Tumblr < Base
+    SIZES = %w[1280 640 540 500h 500 400 250 100]
+
     BASE_URL = %r!\Ahttps?://(?:[^/]+\.)*tumblr\.com!i
     DOMAIN = %r{(data|(\d+\.)?media)\.tumblr\.com}
     MD5 = %r{(?<md5>[0-9a-f]{32})}i
     FILENAME = %r{(?<filename>(tumblr_(inline_)?)?[a-z0-9]+(_r[0-9]+)?)}i
-    SIZES = %r{(?:250|400|500|500h|540|1280|raw)}i
     EXT = %r{(?<ext>\w+)}
-    IMAGE = %r!\Ahttps?://#{DOMAIN}/(?<dir>#{MD5}/)?#{FILENAME}_#{SIZES}\.#{EXT}\z!i
+    IMAGE = %r!\Ahttps?://#{DOMAIN}/(?<dir>#{MD5}/)?#{FILENAME}_(?<size>\w+)\.#{EXT}\z!i
     POST = %r!\Ahttps?://(?<blog_name>[^.]+)\.tumblr\.com/(?:post|image)/(?<post_id>\d+)!i
 
     def self.enabled?
@@ -132,19 +133,16 @@ module Sources::Strategies
     #
     # http://media.tumblr.com/tumblr_m24kbxqKAX1rszquso1_1280.jpg
     # => https://media.tumblr.com/tumblr_m24kbxqKAX1rszquso1_1280.jpg
-    def find_largest(x)
-      if x =~ IMAGE
-        sizes = [1280, 640, 540, "500h", 500, 400, 250]
-        candidates = sizes.map do |size|
-          "https://media.tumblr.com/#{$~[:dir]}#{$~[:filename]}_#{size}.#{$~[:ext]}"
-        end
+    def find_largest(url, sizes: SIZES)
+      return url unless url =~ IMAGE
 
-        return candidates.find do |candidate|
-          http_exists?(candidate, headers)
-        end
+      candidates = sizes.map do |size|
+        "https://media.tumblr.com/#{$~[:dir]}#{$~[:filename]}_#{size}.#{$~[:ext]}"
       end
 
-      return x
+      candidates.find do |candidate|
+        http_exists?(candidate, headers)
+      end
     end
 
     def inline_images
diff --git a/test/unit/sources/tumblr_test.rb b/test/unit/sources/tumblr_test.rb
index 356270ec5..a9873e0c0 100644
--- a/test/unit/sources/tumblr_test.rb
+++ b/test/unit/sources/tumblr_test.rb
@@ -209,5 +209,19 @@ module Sources
         assert_operator(data, :<, site.to_h)
       end
     end
+
+    context "A download for a 'http://*.media.tumblr.com/$hash/tumblr_$id_$size.png' image" do
+      should "find the largest image" do
+        %w[100 250 400 500 500h 540 640 1280].each do |size|
+          page = "https://natsuki-teru.tumblr.com/post/178728919271"
+          image = "https://66.media.tumblr.com/b9395771b2d0435fe4efee926a5a7d9c/tumblr_pg2wu1L9DM1trd056o2_#{size}.png"
+          full = "https://media.tumblr.com/b9395771b2d0435fe4efee926a5a7d9c/tumblr_pg2wu1L9DM1trd056o2_1280.png"
+          site = Sources::Strategies.find(image, page)
+
+          assert_equal(full, site.image_url)
+          assert_equal(full, site.image_urls.second)
+        end
+      end
+    end
   end
 end