diff --git a/Library/Homebrew/extend/pathname.rb b/Library/Homebrew/extend/pathname.rb
index 34f692f28cdec5f8a2ef38e6640554d6d3d6c324..6057c1437488649430f31a19e298c0d88d33f15f 100644
--- a/Library/Homebrew/extend/pathname.rb
+++ b/Library/Homebrew/extend/pathname.rb
@@ -154,21 +154,21 @@ class Pathname
     end
 
     # github tarballs, like v1.2.3
-    %r[github.com/.*/(zip|tar)ball/v?((\d\.)+\d+)$].match to_s
+    %r[github.com/.*/(zip|tar)ball/v?((\d+\.)+\d+)$].match to_s
     return $2 if $2
 
     # eg. https://github.com/sam-github/libnet/tarball/libnet-1.1.4
-    %r[github.com/.*/(zip|tar)ball/.*-((\d\.)+\d+)$].match to_s
+    %r[github.com/.*/(zip|tar)ball/.*-((\d+\.)+\d+)$].match to_s
     return $2 if $2
 
     # dashed version
     # eg. github.com/isaacs/npm/tarball/v0.2.5-1
-    %r[github.com/.*/(zip|tar)ball/v?((\d\.)+\d+-(\d+))$].match to_s
+    %r[github.com/.*/(zip|tar)ball/v?((\d+\.)+\d+-(\d+))$].match to_s
     return $2 if $2
 
     # underscore version
     # eg. github.com/petdance/ack/tarball/1.93_02
-    %r[github.com/.*/(zip|tar)ball/v?((\d\.)+\d+_(\d+))$].match to_s
+    %r[github.com/.*/(zip|tar)ball/v?((\d+\.)+\d+_(\d+))$].match to_s
     return $2 if $2
 
     # eg. boost_1_39_0