diff --git a/plugins/provisioners/salt/provisioner.rb b/plugins/provisioners/salt/provisioner.rb
index 6ec099f1e..118997752 100644
--- a/plugins/provisioners/salt/provisioner.rb
+++ b/plugins/provisioners/salt/provisioner.rb
@@ -136,17 +136,20 @@ module VagrantPlugins
         end
 
         if @config.install_type
-          # Allow passing install_args as an arbitrary string rather
-          # than trying to format it based on known options
-          if @config.install_type != "custom"
-            options = "%s %s" % [options, @config.install_type]
-          end
+          options = "%s %s" % [options, @config.install_type]
         end
 
         if @config.install_args
           options = "%s %s" % [options, @config.install_args]
         end
 
+        if @config.install_command
+          # If this is defined, we will ignore both install_type and
+          # install_args and use this instead. Every necessary command option
+          # will need to be specified by the user.
+          options = @config.install_command
+        end
+
         if @config.verbose
           @machine.env.ui.info "Using Bootstrap Options: %s" % options
         end
diff --git a/website/docs/source/v2/provisioning/salt.html.md b/website/docs/source/v2/provisioning/salt.html.md
index 50bc47656..7dbd9777f 100644
--- a/website/docs/source/v2/provisioning/salt.html.md
+++ b/website/docs/source/v2/provisioning/salt.html.md
@@ -55,10 +55,8 @@ on this machine. Not supported on Windows.
 * `install_syndic`   (boolean) - Install the salt-syndic, default
 `false`. Not supported on Windows.
 
-* `install_type`  (stable | git | daily | testing | custom) - Whether to install from a
+* `install_type`  (stable | git | daily | testing) - Whether to install from a
 distribution's stable package manager, git tree-ish, daily ppa, or testing repository.
-The custom type allows passing an arbitrary string of arguments via `install_args`
-rather than formatting the arguments based on known install types.
 Not supported on Windows.
 
 * `install_args` (develop) - When performing a git install,
@@ -66,6 +64,10 @@ you can specify a branch, tag, or any treeish. If using the `custom` install typ
 you can also specify a different repository to install from.
 Not supported on Windows.
 
+* `install_command` (string) - Allow specifying an arbitrary string of arguments
+to the bootstrap script. This will completely ignore `install_type` and `install_args`
+to allow more flexibility with the bootstrap process.
+
 * `always_install`   (boolean) - Installs salt binaries even
  if they are already detected, default `false`