diff --git a/lib/paneron/register/writeable.rb b/lib/paneron/register/writeable.rb
index e8dfbd9..f687a89 100644
--- a/lib/paneron/register/writeable.rb
+++ b/lib/paneron/register/writeable.rb
@@ -58,8 +58,8 @@ def has_unsynced_changes?
           git_client.gcommit("head").sha
       end
 
-      def commit_changes(message: nil)
-        git_client.commit(message.nil? ? "Sync from ruby-paneron-register" : message)
+      def commit_changes(message = nil)
+        git_client.commit(message.nil? || message.empty? ? "Sync from ruby-paneron-register" : message)
       end
 
       def push_commits_to_remote
@@ -79,7 +79,7 @@ def sync(update: false, message: nil)
           add_changes_to_staging
 
           if has_uncommited_changes?
-            commit_changes(message: message)
+            commit_changes(message)
           end
 
           if has_unsynced_changes?
diff --git a/spec/raw_register_spec.rb b/spec/raw_register_spec.rb
index e866169..8fe7862 100644
--- a/spec/raw_register_spec.rb
+++ b/spec/raw_register_spec.rb
@@ -134,7 +134,7 @@
         allow(raw_register).to receive(:remote?).and_return(true)
         allow(raw_register).to receive(:pull_from_remote)
         allow(raw_register).to receive(:add_changes_to_staging)
-        allow(raw_register).to receive(:commit_changes)
+        allow(raw_register).to receive(:commit_changes).with(optional(String))
         allow(raw_register).to receive(:has_unsynced_changes?)
         allow(raw_register).to receive(:has_uncommited_changes?)
         allow(raw_register).to receive(:push_commits_to_remote)
@@ -157,7 +157,7 @@
           end
 
           it "calls commit_changes" do
-            expect(raw_register).to receive(:commit_changes)
+            expect(raw_register).to receive(:commit_changes).with(optional(String))
             raw_register.sync(update: true)
           end
         end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index fc98c95..6a69ffd 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -27,6 +27,10 @@
 
 # See https://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
 RSpec.configure do |config|
+  def optional(type)
+    satisfy { |value| value.nil? || value.is_a?(type) }
+  end
+
   # rspec-expectations config goes here. You can use an alternate
   # assertion/expectation library such as wrong or the stdlib/minitest
   # assertions if you prefer.