Only check @specs for :using if @specs exists. Fixes Homebrew/homebrew#1127.

1 files changed, 16 insertions, 14 deletions

diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 2bba3d4e7..66219e726 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -134,21 +134,23 @@ class Formula
   
   # reimplement if we don't autodetect the download strategy you require
   def download_strategy
-    vcs = @specs.delete :using
-    if vcs != nil
-      # If a class is passed, assume it is a download strategy
-      return vcs if vcs.kind_of? Class
-
-      case vcs
-      when :bzr then return BazaarDownloadStrategy
-      when :curl then return CurlDownloadStrategy
-      when :cvs then return CVSDownloadStrategy
-      when :git then return GitDownloadStrategy
-      when :hg then return MercurialDownloadStrategy
-      when :svn then return SubversionDownloadStrategy
-      end
+    if @specs
+      vcs = @specs.delete :using
+      if vcs != nil
+        # If a class is passed, assume it is a download strategy
+        return vcs if vcs.kind_of? Class
+
+        case vcs
+        when :bzr then return BazaarDownloadStrategy
+        when :curl then return CurlDownloadStrategy
+        when :cvs then return CVSDownloadStrategy
+        when :git then return GitDownloadStrategy
+        when :hg then return MercurialDownloadStrategy
+        when :svn then return SubversionDownloadStrategy
+        end
 
-      raise "Unknown strategy #{vcs} was requested."
+        raise "Unknown strategy #{vcs} was requested."
+      end
     end
 
     detect_download_strategy url