diff --git a/Library/Homebrew/build.rb b/Library/Homebrew/build.rb
index c4e903642b..c0f15158d1 100644
--- a/Library/Homebrew/build.rb
+++ b/Library/Homebrew/build.rb
@@ -48,7 +48,7 @@ class Build
         Requirement.prune
       elsif req.build? && dependent != formula
         Requirement.prune
-      elsif req.satisfied? && req.default_formula? && (dep = req.to_dependency).installed?
+      elsif req.satisfied? && (dep = req.to_dependency) && dep.installed?
         deps << dep
         Requirement.prune
       end
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 91a3e8150d..1ced5030fc 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -1519,10 +1519,15 @@ class Formula
   # Returns a list of Dependency objects that are required at runtime.
   # @private
   def runtime_dependencies
-    recursive_dependencies do |_dependent, dependency|
+    runtime_dependencies = recursive_dependencies do |_, dependency|
       Dependency.prune if dependency.build?
       Dependency.prune if !dependency.required? && build.without?(dependency)
     end
+    runtime_requirement_deps = recursive_requirements do |_, requirement|
+      Requirement.prune if requirement.build?
+      Requirement.prune if !requirement.required? && build.without?(requirement)
+    end.map(&:to_dependency).compact
+    runtime_dependencies + runtime_requirement_deps
   end
 
   # Returns a list of formulae depended on by this formula that aren't
diff --git a/Library/Homebrew/formula_installer.rb b/Library/Homebrew/formula_installer.rb
index 115d38c45f..55e9832648 100644
--- a/Library/Homebrew/formula_installer.rb
+++ b/Library/Homebrew/formula_installer.rb
@@ -370,8 +370,8 @@ class FormulaInstaller
     raise UnsatisfiedRequirements, fatals
   end
 
-  def install_requirement_default_formula?(req, dependent, build)
-    return false unless req.default_formula?
+  def install_requirement_formula?(req, dependent, build)
+    return false unless req.to_dependency
     return true unless req.satisfied?
     return false if req.run?
     install_bottle_for?(dependent, build) || build_bottle?
@@ -390,7 +390,7 @@ class FormulaInstaller
           Requirement.prune
         elsif req.build? && install_bottle_for?(dependent, build)
           Requirement.prune
-        elsif install_requirement_default_formula?(req, dependent, build)
+        elsif install_requirement_formula?(req, dependent, build)
           dep = req.to_dependency
           deps.unshift(dep)
           formulae.unshift(dep.to_formula)
diff --git a/Library/Homebrew/requirement.rb b/Library/Homebrew/requirement.rb
index fe1a3c020f..49108ca75a 100644
--- a/Library/Homebrew/requirement.rb
+++ b/Library/Homebrew/requirement.rb
@@ -15,6 +15,7 @@ class Requirement
     @default_formula = self.class.default_formula
     @cask ||= self.class.cask
     @download ||= self.class.download
+    @formula = nil
     tags.each do |tag|
       next unless tag.is_a? Hash
       @cask ||= tag[:cask]
@@ -56,7 +57,14 @@ class Requirement
   def satisfied?
     result = self.class.satisfy.yielder { |p| instance_eval(&p) }
     @satisfied_result = result
-    result ? true : false
+    return false unless result
+
+    if parent = satisfied_result_parent
+      parent.to_s =~ %r{(#{Regexp.escape(HOMEBREW_CELLAR)}|#{Regexp.escape(HOMEBREW_PREFIX)}/opt)/([\w+-.@]+)}
+      @formula = $2
+    end
+
+    true
   end
 
   # Overriding #fatal? is deprecated.
@@ -69,6 +77,11 @@ class Requirement
     self.class.default_formula || false
   end
 
+  def satisfied_result_parent
+    return unless @satisfied_result.is_a?(Pathname)
+    @satisfied_result.resolved_path.parent
+  end
+
   # Overriding #modify_build_environment is deprecated.
   # Pass a block to the env DSL method instead.
   # Note: #satisfied? should be called before invoking this method
@@ -81,11 +94,8 @@ class Requirement
     #   satisfy { which("executable") }
     # work, even under superenv where "executable" wouldn't normally be on the
     # PATH.
-    # This is undocumented magic and it should be removed, but we need to add
-    # a way to declare path-based requirements that work with superenv first.
-    return unless @satisfied_result.is_a?(Pathname)
-    parent = @satisfied_result.parent
-
+    parent = satisfied_result_parent
+    return unless parent
     return if ENV["PATH"].split(File::PATH_SEPARATOR).include?(parent.to_s)
     ENV.append_path("PATH", parent)
   end
@@ -111,13 +121,15 @@ class Requirement
     "#<#{self.class.name}: #{name.inspect} #{tags.inspect}>"
   end
 
+  def formula
+    @formula || self.class.default_formula
+  end
+
   def to_dependency
-    f = self.class.default_formula
-    raise "No default formula defined for #{inspect}" if f.nil?
-    if f =~ HOMEBREW_TAP_FORMULA_REGEX
-      TapDependency.new(f, tags, method(:modify_build_environment), name)
-    else
-      Dependency.new(f, tags, method(:modify_build_environment), name)
+    if formula =~ HOMEBREW_TAP_FORMULA_REGEX
+      TapDependency.new(formula, tags, method(:modify_build_environment), name)
+    elsif formula
+      Dependency.new(formula, tags, method(:modify_build_environment), name)
     end
   end