diff --git a/lib/ruby_git.rb b/lib/ruby_git.rb
index a3ac9b6..e94403b 100644
--- a/lib/ruby_git.rb
+++ b/lib/ruby_git.rb
@@ -3,6 +3,7 @@
 require_relative 'ruby_git/command_line'
 require_relative 'ruby_git/encoding_normalizer'
 require_relative 'ruby_git/errors'
+require_relative 'ruby_git/option_validators'
 require_relative 'ruby_git/repository'
 require_relative 'ruby_git/status'
 require_relative 'ruby_git/version'
diff --git a/lib/ruby_git/command_line/runner.rb b/lib/ruby_git/command_line/runner.rb
index fd3b9cb..03fa66d 100644
--- a/lib/ruby_git/command_line/runner.rb
+++ b/lib/ruby_git/command_line/runner.rb
@@ -187,20 +187,39 @@ def call(*args, **options_hash)
       #
       # @api private
       #
-      def run_with_chdir(args, options)
-        return ProcessExecuter.run_with_options(args, options) unless jruby? && options.chdir != :not_set
+      def run_with_chdir(args, options) # rubocop:disable Metrics/MethodLength
+        return run_and_handle_spawn_error(args, options) unless jruby? && options.chdir != :not_set
 
         # :nocov: Not executed in MRI Ruby
-        Dir.chdir(options.chdir) do
-          saved_chdir = options.chdir
-          options.merge!(chdir: :not_set)
-          ProcessExecuter.run_with_options(args, options).tap do
-            options.merge!(chdir: saved_chdir)
+        begin
+          Dir.chdir(options.chdir) do
+            saved_chdir = options.chdir
+            options.merge!(chdir: :not_set)
+            run_and_handle_spawn_error(args, options).tap do
+              options.merge!(chdir: saved_chdir)
+            end
           end
+        rescue Errno::ENOENT, Errno::ENOTDIR => e
+          raise RubyGit::SpawnError, "chdir(#{options.chdir}) failed: #{e.message}"
         end
         # :nocov:
       end
 
+      # Catch ProcessExecuter::SpawnError and raise a RubyGit::SpawnError in its place
+      #
+      # @param args [Array<String>] the command to run
+      # @param options [RubyGit::CommandLine::Options] the options to pass to `Process.spawn`
+      #
+      # @return [ProcessExecuter::Result] the result of the command
+      #
+      # @api private
+      #
+      def run_and_handle_spawn_error(args, options)
+        ProcessExecuter.run_with_options(args, options)
+      rescue ProcessExecuter::SpawnError => e
+        raise RubyGit::SpawnError, e.message
+      end
+
       # Returns true if running on JRuby
       #
       # @return [Boolean]
diff --git a/lib/ruby_git/errors.rb b/lib/ruby_git/errors.rb
index 4384342..574b95c 100644
--- a/lib/ruby_git/errors.rb
+++ b/lib/ruby_git/errors.rb
@@ -21,6 +21,7 @@ module RubyGit
   #     │   └─> RubyGit::SignaledError
   #     │       └─> RubyGit::TimeoutError
   #     ├─> RubyGit::ProcessIOError
+  #     ├─> RubyGit::SpawnError
   #     └─> RubyGit::UnexpectedResultError
   # ```
   #
@@ -32,6 +33,7 @@ module RubyGit
   # | `SignaledError` | This error is raised when the git command line is terminated as a result of receiving a signal. This could happen if the process is forcibly terminated or if there is a serious system error. |
   # | `TimeoutError` | This is a specific type of `SignaledError` that is raised when the git command line operation times out and is killed via the SIGKILL signal. This happens if the operation takes longer than the timeout duration configured in `Git.config.timeout` or via the `:timeout` parameter given in git methods that support timeouts. |
   # | `ProcessIOError` | An error was encountered reading or writing to a subprocess. |
+  # | `SpawnError` | An error was encountered when spawning a subprocess and it never started. |
   # | `UnexpectedResultError` | The command line ran without error but did not return the expected results. |
   #
   # @example Rescuing a generic error
@@ -166,4 +168,10 @@ class ProcessIOError < RubyGit::Error; end
   # @api public
   #
   class UnexpectedResultError < RubyGit::Error; end
+
+  # Raised when the git command could not be spawned
+  #
+  # @api public
+  #
+  class SpawnError < RubyGit::Error; end
 end
diff --git a/lib/ruby_git/option_validators.rb b/lib/ruby_git/option_validators.rb
new file mode 100644
index 0000000..4645783
--- /dev/null
+++ b/lib/ruby_git/option_validators.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+module RubyGit
+  # Module containing option validators for RubyGit
+  # @api public
+  module OptionValidators
+    # Raise an error if an option is not a Boolean (or optionally nil) value
+    # @param name [String] the name of the option
+    # @param value [Object] the value of the option
+    # @param nullable [Boolean] whether the option can be nil (default is false)
+    # @return [void]
+    # @raise [ArgumentError] if the option is not a Boolean (or optionally nil) value
+    # @api private
+    def validate_boolean_option(name:, value:, nullable: false)
+      return if nullable && value.nil?
+
+      return if [true, false].include?(value)
+
+      raise ArgumentError, "The '#{name}:' option must be a Boolean value but was #{value.inspect}"
+    end
+
+    # Raise an error if an option is not a String (or optionally nil) value
+    # @param name [String] the name of the option
+    # @param value [Object] the value of the option
+    # @param nullable [Boolean] whether the option can be nil (default is false)
+    # @return [void]
+    # @raise [ArgumentError] if the option is not a String (or optionally nil) value
+    # @api private
+    def validate_string_option(name:, value:, nullable: false)
+      return if nullable && value.nil?
+
+      return if value.is_a?(String)
+
+      raise ArgumentError, "The '#{name}:' option must be a String or nil but was #{value.inspect}"
+    end
+  end
+end
diff --git a/lib/ruby_git/worktree.rb b/lib/ruby_git/worktree.rb
index 46ffff4..567c720 100644
--- a/lib/ruby_git/worktree.rb
+++ b/lib/ruby_git/worktree.rb
@@ -7,6 +7,9 @@ module RubyGit
   # Create a new Worktree using {.init}, {.clone}, or {.open}.
   #
   class Worktree
+    extend RubyGit::OptionValidators
+    include RubyGit::OptionValidators
+
     # The root path of the working tree
     #
     # @example
@@ -28,17 +31,22 @@ class Worktree
     # @example
     #   worktree = Worktree.init(worktree_path)
     #
-    # @param [String] worktree_path the root path of a Git working tree
+    # @param worktree_path [String] the root path of a Git working tree
+    # @param initial_branch [String] the initial branch in the newly created repository
     #
-    # @raise [RubyGit::Error] if worktree_path is not a directory
+    # @raise [ArgumentError] if worktree_path does not exist or is not a directory
+    # @raise [RubyGit::Error] if there is an error initializing the repository
     #
     # @return [RubyGit::Worktree] the working tree whose root is at `path`
     #
-    def self.init(worktree_path)
-      raise RubyGit::Error, "Path '#{worktree_path}' not valid." unless File.directory?(worktree_path)
+    def self.init(worktree_path, initial_branch: nil)
+      validate_string_option(name: :initial_branch, value: initial_branch, nullable: true)
 
       command = ['init']
+      command << '--initial-branch' << initial_branch unless initial_branch.nil?
+
       options = { chdir: worktree_path, out: StringIO.new, err: StringIO.new }
+
       RubyGit::CommandLine.run(*command, **options)
 
       new(worktree_path)
@@ -300,20 +308,5 @@ def root_path(worktree_path)
     def run_with_context(*command, **options)
       RubyGit::CommandLine.run(*command, repository_path: repository.path, worktree_path: path, **options)
     end
-
-    # Raise an error if an option is not a Boolean (or optionally nil) value
-    # @param name [String] the name of the option
-    # @param value [Object] the value of the option
-    # @param nullable [Boolean] whether the option can be nil (default is false)
-    # @return [void]
-    # @raise [ArgumentError] if the option is not a Boolean (or optionally nil) value
-    # @api private
-    def validate_boolean_option(name:, value:, nullable: false)
-      return if nullable && value.nil?
-
-      return if [true, false].include?(value)
-
-      raise ArgumentError, "The '#{name}:' option must be a Boolean value but was #{value.inspect}"
-    end
   end
 end
diff --git a/spec/lib/ruby_git/worktree_init_spec.rb b/spec/lib/ruby_git/worktree_init_spec.rb
index 58fcdfd..3d8b238 100644
--- a/spec/lib/ruby_git/worktree_init_spec.rb
+++ b/spec/lib/ruby_git/worktree_init_spec.rb
@@ -3,46 +3,119 @@
 require 'tmpdir'
 
 RSpec.describe RubyGit::Worktree do
-  describe '.init(worktree_path)' do
-    subject { described_class.init(worktree_path) }
-    let(:tmpdir) { Dir.mktmpdir }
-    after { FileUtils.rm_rf(tmpdir) }
-
-    context 'when worktree_path does not exist' do
-      let(:worktree_path) { tmpdir }
-      before { FileUtils.rmdir(tmpdir) }
-      it 'should raise a RubyGit::Error' do
-        expect { subject }.to raise_error(RubyGit::Error)
-      end
-    end
+  describe '.init' do
+    subject { described_class.init(worktree_path, initial_branch: initial_branch) }
+    let(:initial_branch) { nil }
+
+    describe 'initializing a worktree' do
+      let(:tmpdir) { @tmpdir }
 
-    context 'when worktree_path exists' do
-      let(:worktree_path) { tmpdir }
-      context 'and is not a directory' do
-        before do
-          FileUtils.rmdir(worktree_path)
-          FileUtils.touch(worktree_path)
+      around do |example|
+        in_temp_dir do |tmpdir|
+          @tmpdir = tmpdir
+          example.run
         end
-        it 'should raise RubyGit::Error' do
-          expect { subject }.to raise_error(RubyGit::Error)
+      end
+
+      context 'when worktree_path does not exist' do
+        let(:worktree_path) { File.join(tmpdir, 'subdir') }
+
+        expected_error = truffleruby? ? RubyGit::FailedError : RubyGit::SpawnError
+
+        it "should raise an error #{expected_error}" do
+          expect { subject }.to raise_error(expected_error)
         end
       end
 
-      context 'and is a directory' do
-        context 'and is in a working tree' do
+      context 'when worktree_path exists' do
+        let(:worktree_path) { tmpdir }
+        context 'and is not a directory' do
           before do
-            raise RuntimeError unless system('git init', chdir: worktree_path, %i[out err] => IO::NULL)
+            FileUtils.rmdir(worktree_path)
+            FileUtils.touch(worktree_path)
           end
-          it 'should return a Worktree object to the existing working tree' do
-            expect(subject).to be_kind_of(RubyGit::Worktree)
-            expect(subject).to have_attributes(path: File.realpath(worktree_path))
+
+          expected_error = truffleruby? ? RubyGit::FailedError : RubyGit::SpawnError
+
+          it "should raise a #{expected_error} " do
+            expect { subject }.to raise_error(expected_error)
           end
         end
 
-        context 'and is not in the working tree' do
-          it 'should initialize the working tree and return a Worktree object' do
-            expect(subject).to be_kind_of(RubyGit::Worktree)
-            expect(subject).to have_attributes(path: File.realpath(worktree_path))
+        context 'and is a directory' do
+          context 'and is in a working tree' do
+            before do
+              raise RuntimeError unless system('git init', chdir: worktree_path, %i[out err] => IO::NULL)
+            end
+            it 'should return a Worktree object to the existing working tree' do
+              expect(subject).to be_kind_of(RubyGit::Worktree)
+              expect(subject).to have_attributes(path: File.realpath(worktree_path))
+            end
+          end
+
+          context 'and is not in the working tree' do
+            it 'should initialize the working tree and return a Worktree object' do
+              expect(subject).to be_kind_of(RubyGit::Worktree)
+              expect(subject).to have_attributes(path: File.realpath(worktree_path))
+            end
+          end
+        end
+      end
+    end
+
+    describe 'constructing the git command line' do
+      let(:worktree_path) { '/my/worktree/path' }
+      let(:result) { instance_double(RubyGit::CommandLine::Result, stdout: '') }
+
+      before do
+        allow(described_class).to(
+          receive(:new).with(worktree_path).and_return(instance_double(RubyGit::Worktree))
+        )
+      end
+
+      context 'called with no arguments' do
+        let(:expected_command) { %w[init] }
+
+        it 'should run the expected git command' do
+          expect(RubyGit::CommandLine).to(
+            receive(:run).with(*expected_command, Hash).and_return(result)
+          )
+
+          subject
+        end
+      end
+
+      describe 'initial_branch option' do
+        context 'when nil' do
+          let(:expected_command) { %w[init] }
+
+          it 'should run the expected git command' do
+            expect(RubyGit::CommandLine).to(
+              receive(:run).with(*expected_command, Hash).and_return(result)
+            )
+            subject
+          end
+        end
+
+        context 'when a string' do
+          let(:expected_command) { ['init', '--initial-branch', initial_branch] }
+          let(:initial_branch) { 'my-branch' }
+
+          it 'should run the expected git command' do
+            expect(RubyGit::CommandLine).to(
+              receive(:run).with(*expected_command, Hash).and_return(result)
+            )
+            subject
+          end
+        end
+
+        context 'when not a string' do
+          let(:initial_branch) { 123 }
+
+          it 'should raise an ArgumentError' do
+            expect { subject }.to(
+              raise_error(ArgumentError, %(The 'initial_branch:' option must be a String or nil but was 123))
+            )
           end
         end
       end