diff --git a/Library/Homebrew/tap_constants.rb b/Library/Homebrew/tap_constants.rb
index 1757ab80e7..d706d85296 100644
--- a/Library/Homebrew/tap_constants.rb
+++ b/Library/Homebrew/tap_constants.rb
@@ -1,7 +1,7 @@
 # match expressions when taps are given as ARGS, e.g. someuser/sometap
 HOMEBREW_TAP_ARGS_REGEX = %r{^([\w-]+)/(homebrew-)?([\w-]+)$}
 # match taps' formula, e.g. someuser/sometap/someformula
-HOMEBREW_TAP_FORMULA_REGEX = %r{^([\w-]+)/([\w-]+)/([\w-]+)$}
+HOMEBREW_TAP_FORMULA_REGEX = %r{^([\w-]+)/([\w-]+)/([\w+-]+)$}
 # match taps' directory path, e.g. HOMEBREW_LIBRARY/Taps/someuser/sometap
 HOMEBREW_TAP_DIR_REGEX = %r{#{HOMEBREW_LIBRARY}/Taps/([\w-]+)/([\w-]+)}
 # match taps' formula path, e.g. HOMEBREW_LIBRARY/Taps/someuser/sometap/someformula