diff --git a/Library/Homebrew/cmd/tap.rb b/Library/Homebrew/cmd/tap.rb
index 656dc20768..279dde75c6 100644
--- a/Library/Homebrew/cmd/tap.rb
+++ b/Library/Homebrew/cmd/tap.rb
@@ -60,7 +60,8 @@ module Homebrew
                     quiet:             args.quieter?
       rescue TapRemoteMismatchError => e
         odie e
-      rescue TapAlreadyTappedError, TapAlreadyUnshallowError # rubocop:disable Lint/SuppressedException
+      rescue TapAlreadyTappedError
+        nil
       end
     end
   end
diff --git a/Library/Homebrew/exceptions.rb b/Library/Homebrew/exceptions.rb
index 55fa41db68..3c81060a06 100644
--- a/Library/Homebrew/exceptions.rb
+++ b/Library/Homebrew/exceptions.rb
@@ -258,18 +258,6 @@ class TapAlreadyTappedError < RuntimeError
   end
 end
 
-class TapAlreadyUnshallowError < RuntimeError
-  attr_reader :name
-
-  def initialize(name)
-    @name = name
-
-    super <<~EOS
-      Tap #{name} already a full clone.
-    EOS
-  end
-end
-
 class TapPinStatusError < RuntimeError
   attr_reader :name, :pinned
 
diff --git a/Library/Homebrew/tap.rb b/Library/Homebrew/tap.rb
index b5c8550263..6e6824f98a 100644
--- a/Library/Homebrew/tap.rb
+++ b/Library/Homebrew/tap.rb
@@ -233,7 +233,7 @@ class Tap
   def install(options = {})
     require "descriptions"
 
-    full_clone = options.fetch(:full_clone, false)
+    full_clone = options.fetch(:full_clone, true)
     quiet = options.fetch(:quiet, false)
     requested_remote = options[:clone_target] || default_remote
     # if :force_auto_update is unset, use nil, meaning "no change"
@@ -245,9 +245,12 @@ class Tap
       odie "#{name} was moved. Tap homebrew/cask-#{repo} instead."
     end
 
-    if installed? && force_auto_update.nil?
-      raise TapAlreadyTappedError, name unless full_clone
-      raise TapAlreadyUnshallowError, name unless shallow?
+    if installed?
+      if options[:clone_target] && requested_remote != remote
+        raise TapRemoteMismatchError.new(name, @remote, requested_remote)
+      end
+
+      raise TapAlreadyTappedError, name if force_auto_update.nil?
     end
 
     # ensure git is installed
@@ -259,10 +262,6 @@ class Tap
         return if !full_clone || !shallow?
       end
 
-      if options[:clone_target] && requested_remote != remote
-        raise TapRemoteMismatchError.new(name, @remote, requested_remote)
-      end
-
       ohai "Unshallowing #{name}" unless quiet
       args = %w[fetch --unshallow]
       args << "-q" if quiet
diff --git a/Library/Homebrew/test/tap_spec.rb b/Library/Homebrew/test/tap_spec.rb
index 2a6f1d6dea..4a14ee081d 100644
--- a/Library/Homebrew/test/tap_spec.rb
+++ b/Library/Homebrew/test/tap_spec.rb
@@ -207,7 +207,6 @@ describe Tap do
     it "raises an error when the remote doesn't match" do
       setup_git_repo
       already_tapped_tap = described_class.new("Homebrew", "foo")
-      touch subject.path/".git/shallow"
       expect(already_tapped_tap).to be_installed
       wrong_remote = "#{subject.remote}-oops"
       expect {
@@ -215,12 +214,6 @@ describe Tap do
       }.to raise_error(TapRemoteMismatchError)
     end
 
-    it "raises an error when the Tap is already unshallow" do
-      setup_git_repo
-      already_tapped_tap = described_class.new("Homebrew", "foo")
-      expect { already_tapped_tap.install full_clone: true }.to raise_error(TapAlreadyUnshallowError)
-    end
-
     describe "force_auto_update" do
       before do
         setup_git_repo