diff --git a/Library/Homebrew/cmd/tap.rb b/Library/Homebrew/cmd/tap.rb
index 91f873e679..addde2b4af 100644
--- a/Library/Homebrew/cmd/tap.rb
+++ b/Library/Homebrew/cmd/tap.rb
@@ -25,8 +25,10 @@ module Homebrew
         using protocols other than HTTPS, e.g. SSH, git, HTTP, FTP(S), rsync.
       EOS
       switch "--full",
-             description: "Convert a shallow clone to a full clone without untapping. By default, taps are no "\
-                          "longer cloned as shallow clones."
+             description: "Convert a shallow clone to a full clone without untapping. Taps are only cloned as "\
+                          "shallow clones on continuous integration, or if `--shallow` was originally passed."
+      switch "--shallow",
+             description: "Fetch tap as a shallow clone rather than a full clone. Useful for continuous integration."
       switch "--force-auto-update",
              description: "Auto-update tap even if it is not hosted on GitHub. By default, only taps "\
                           "hosted on GitHub are auto-updated (for performance reasons)."
@@ -51,11 +53,20 @@ module Homebrew
     elsif args.no_named?
       puts Tap.names
     else
+      full_clone = if args.full?
+        true
+      elsif !args.shallow?
+        ENV["CI"].blank?
+      else
+        !args.shallow?
+      end
+      odebug "Tapping as #{full_clone ? "full" : "shallow"} clone"
       tap = Tap.fetch(args.named.first)
       begin
         tap.install clone_target:      args.named.second,
                     force_auto_update: force_auto_update?,
-                    quiet:             args.quiet?
+                    quiet:             args.quiet?,
+                    full_clone:        full_clone
       rescue TapRemoteMismatchError => e
         odie e
       rescue TapAlreadyTappedError
diff --git a/Library/Homebrew/tap.rb b/Library/Homebrew/tap.rb
index 8721bbe0e7..9894b4b47b 100644
--- a/Library/Homebrew/tap.rb
+++ b/Library/Homebrew/tap.rb
@@ -243,7 +243,7 @@ class Tap
 
     if installed?
       raise TapRemoteMismatchError.new(name, @remote, requested_remote) if clone_target && requested_remote != remote
-      raise TapAlreadyTappedError, name if force_auto_update.nil?
+      raise TapAlreadyTappedError, name if force_auto_update.nil? && !shallow?
     end
 
     # ensure git is installed
diff --git a/docs/Manpage.md b/docs/Manpage.md
index cb084c827a..9ec3a9f0ed 100644
--- a/docs/Manpage.md
+++ b/docs/Manpage.md
@@ -501,7 +501,9 @@ taps can be cloned from places other than GitHub and using protocols other than
 HTTPS, e.g. SSH, git, HTTP, FTP(S), rsync.
 
 * `--full`:
-  Convert a shallow clone to a full clone without untapping. By default, taps are no longer cloned as shallow clones.
+  Convert a shallow clone to a full clone without untapping. Taps are only cloned as shallow clones on continuous integration, or if `--shallow` was originally passed.
+* `--shallow`:
+  Fetch tap as a shallow clone rather than a full clone. Useful for continuous integration.
 * `--force-auto-update`:
   Auto-update tap even if it is not hosted on GitHub. By default, only taps hosted on GitHub are auto-updated (for performance reasons).
 * `--repair`:
diff --git a/manpages/brew.1 b/manpages/brew.1
index 366176d59c..49c9bf8809 100644
--- a/manpages/brew.1
+++ b/manpages/brew.1
@@ -635,7 +635,11 @@ With \fIURL\fR specified, tap a formula repository from anywhere, using any tran
 .
 .TP
 \fB\-\-full\fR
-Convert a shallow clone to a full clone without untapping\. By default, taps are no longer cloned as shallow clones\.
+Convert a shallow clone to a full clone without untapping\. Taps are only cloned as shallow clones on continuous integration, or if \fB\-\-shallow\fR was originally passed\.
+.
+.TP
+\fB\-\-shallow\fR
+Fetch tap as a shallow clone rather than a full clone\. Useful for continuous integration\.
 .
 .TP
 \fB\-\-force\-auto\-update\fR