diff --git a/Library/Homebrew/dependency.rb b/Library/Homebrew/dependency.rb
index 3a203e8960..05318fc9ad 100644
--- a/Library/Homebrew/dependency.rb
+++ b/Library/Homebrew/dependency.rb
@@ -100,7 +100,7 @@ class Dependency
       grouped = deps.group_by(&:name)
 
       deps.uniq.map do |dep|
-        tags = grouped.fetch(dep.name).map(&:tags).flatten
+        tags = grouped.fetch(dep.name).map(&:tags).flatten.uniq
         merged_dep = dep.class.new(dep.name, tags)
         merged_dep.env_proc = dep.env_proc
         merged_dep
diff --git a/Library/Homebrew/test/test_dependency_expansion.rb b/Library/Homebrew/test/test_dependency_expansion.rb
index a6b9cbdec5..d0dada2e07 100644
--- a/Library/Homebrew/test/test_dependency_expansion.rb
+++ b/Library/Homebrew/test/test_dependency_expansion.rb
@@ -74,4 +74,12 @@ class DependencyExpansionTests < Test::Unit::TestCase
     env_proc = @foo.env_proc = stub
     assert_equal env_proc, Dependency.expand(@f).first.env_proc
   end
+
+  def test_merged_tags_no_dupes
+    @foo2 = build_dep(:foo, ['option'])
+    @foo3 = build_dep(:foo, ['option'])
+    @deps << @foo2 << @foo3
+
+    assert_equal %w{option}, Dependency.expand(@f).first.tags
+  end
 end