diff --git a/lib/rack/show_exceptions.rb b/lib/rack/show_exceptions.rb
index ca86b2b2a..ef30fce43 100644
--- a/lib/rack/show_exceptions.rb
+++ b/lib/rack/show_exceptions.rb
@@ -46,7 +46,7 @@ def call(env)
     end
 
     def prefers_plaintext?(env)
-      !accepts_html(env)
+      !accepts_html?(env)
     end
 
     def accepts_html?(env)
diff --git a/test/spec_show_exceptions.rb b/test/spec_show_exceptions.rb
index cd44c8168..61e5d92d6 100644
--- a/test/spec_show_exceptions.rb
+++ b/test/spec_show_exceptions.rb
@@ -77,4 +77,17 @@ def show_exceptions(app)
     assert_match(res, /ShowExceptions/)
     assert_match(res, /unknown location/)
   end
+
+  it "knows to prefer plaintext for non-html" do
+    # We don't need an app for this
+    exc = Rack::ShowExceptions.new(nil)
+
+    [
+      [{ "HTTP_ACCEPT" => "text/plain" }, true],
+      [{ "HTTP_ACCEPT" => "text/foo" }, true],
+      [{ "HTTP_ACCEPT" => "text/html" }, false]
+    ].each do |env, expected|
+      assert_equal(expected, exc.prefers_plaintext?(env))
+    end
+  end
 end