diff --git a/Formula/ginac.rb b/Formula/ginac.rb
index d7351578a5d..3b1c710a10a 100644
--- a/Formula/ginac.rb
+++ b/Formula/ginac.rb
@@ -10,8 +10,9 @@ class Ginac < Formula
   depends_on 'readline'
 
   # Fixes compilation with libc++; already applied upstream
-  def patches
-    "http://www.ginac.de/ginac.git?p=ginac.git;a=commitdiff_plain;h=5bf87cea66bb2071222c2910ed68c2649a98906c"
+  patch do
+    url "http://www.ginac.de/ginac.git?p=ginac.git;a=commitdiff_plain;h=5bf87cea66bb2071222c2910ed68c2649a98906c"
+    sha1 "415dad5f0f233268ad743e5beacf99c03bb339ae"
   end
 
   def install