diff --git a/Formula/coreutils.rb b/Formula/coreutils.rb
index 8fc1a06ac0..4d001469d2 100644
--- a/Formula/coreutils.rb
+++ b/Formula/coreutils.rb
@@ -6,6 +6,8 @@ class Coreutils < Formula
   mirror 'http://ftp.gnu.org/gnu/coreutils/coreutils-8.21.tar.xz'
   sha256 'adaa44bdab3fa5eb352e80d8a31fdbf957b78653d0c2cd30d63e161444288e18'
 
+  conflicts_with 'idutils', :because => 'both install `gid` and `gid.1`'
+
   depends_on 'xz' => :build
 
   def install
diff --git a/Formula/idutils.rb b/Formula/idutils.rb
index 4e2f7b5c55..cb3ee1f271 100644
--- a/Formula/idutils.rb
+++ b/Formula/idutils.rb
@@ -6,6 +6,8 @@ class Idutils < Formula
   mirror 'http://ftp.gnu.org/gnu/idutils/idutils-4.6.tar.xz'
   sha256 '8181f43a4fb62f6f0ccf3b84dbe9bec71ecabd6dfdcf49c6b5584521c888aac2'
 
+  conflicts_with 'coreutils', :because => 'both install `gid` and `gid.1`'
+
   depends_on 'xz' => :build
 
   def install