diff --git a/Library/Homebrew/keg.rb b/Library/Homebrew/keg.rb
index 1de4ce1f0c..3d2d21d692 100644
--- a/Library/Homebrew/keg.rb
+++ b/Library/Homebrew/keg.rb
@@ -139,6 +139,10 @@ class Keg
     raise NotAKegError, "#{path} is not inside a keg"
   end
 
+  def self.all
+    Formula.racks.flat_map(&:subdirs).map { |d| new(d) }
+  end
+
   attr_reader :path, :name, :linked_keg_record, :opt_record
   protected :path
 
@@ -353,14 +357,21 @@ class Keg
   end
 
   def installed_dependents
-    Formula.installed.flat_map(&:installed_kegs).select do |keg|
+    my_tab = Tab.for_keg(self)
+    Keg.all.select do |keg|
       tab = Tab.for_keg(keg)
       next if tab.runtime_dependencies.nil? # no dependency information saved.
       tab.runtime_dependencies.any? do |dep|
         # Resolve formula rather than directly comparing names
         # in case of conflicts between formulae from different taps.
-        dep_formula = Formulary.factory(dep["full_name"])
-        dep_formula == to_formula && dep["version"] == version.to_s
+        begin
+          dep_formula = Formulary.factory(dep["full_name"])
+          next false unless dep_formula == to_formula
+        rescue FormulaUnavailableError
+          next false unless my_tab["full_name"] = dep["full_name"]
+        end
+
+        dep["version"] == version.to_s
       end
     end
   end
diff --git a/Library/Homebrew/test/keg_test.rb b/Library/Homebrew/test/keg_test.rb
index b875c7205b..cf5f13a6c9 100644
--- a/Library/Homebrew/test/keg_test.rb
+++ b/Library/Homebrew/test/keg_test.rb
@@ -47,6 +47,11 @@ class LinkTestCase < Homebrew::TestCase
 end
 
 class LinkTests < LinkTestCase
+  def test_all
+    Formula.clear_racks_cache
+    assert_equal [@keg], Keg.all
+  end
+
   def test_empty_installation
     %w[.DS_Store INSTALL_RECEIPT.json LICENSE.txt].each do |file|
       touch @keg/file
@@ -355,10 +360,11 @@ class InstalledDependantsTests < LinkTestCase
   # from a file path or URL.
   def test_unknown_formula
     Formulary.unstub(:loader_for)
-    dependencies []
+    alter_tab { |t| t.source["tap"] = "some/tap" }
+    dependencies [{ "full_name" => "some/tap/bar", "version" => "1.0" }]
     alter_tab { |t| t.source["path"] = nil }
-    assert_empty @keg.installed_dependents
-    assert_nil Keg.find_some_installed_dependents([@keg])
+    assert_equal [@dependent], @keg.installed_dependents
+    assert_equal [[@keg], ["bar 1.0"]], Keg.find_some_installed_dependents([@keg])
   end
 
   def test_no_dependencies_anywhere