diff --git a/Library/Homebrew/extend/ENV/super.rb b/Library/Homebrew/extend/ENV/super.rb
index 3ac9ffeded..38bf75789f 100644
--- a/Library/Homebrew/extend/ENV/super.rb
+++ b/Library/Homebrew/extend/ENV/super.rb
@@ -74,6 +74,7 @@ module Superenv
     self["CMAKE_INCLUDE_PATH"] = determine_cmake_include_path
     self["CMAKE_LIBRARY_PATH"] = determine_cmake_library_path
     self["ACLOCAL_PATH"] = determine_aclocal_path
+    self["M4"] = "#{HOMEBREW_PREFIX}/opt/m4/bin/m4" if deps.any? { |d| d.name == "libtool" }
     self["HOMEBREW_ISYSTEM_PATHS"] = determine_isystem_paths
     self["HOMEBREW_INCLUDE_PATHS"] = determine_include_paths
     self["HOMEBREW_LIBRARY_PATHS"] = determine_library_paths