diff --git a/PBGitCommitController.m b/PBGitCommitController.m
index f41ffe2..d74e2a5 100644
--- a/PBGitCommitController.m
+++ b/PBGitCommitController.m
@@ -318,6 +318,11 @@
 
 - (IBAction) commit:(id) sender
 {
+	if ([[NSFileManager defaultManager] fileExistsAtPath:[repository.fileURL.path stringByAppendingPathComponent:@"MERGE_HEAD"]]) {
+		[[repository windowController] showMessageSheet:@"Cannot commit merges" infoText:@"GitX cannot commit merges yet. Please commit your changes from the command line."];
+		return;
+	}
+
 	if ([[cachedFilesController arrangedObjects] count] == 0) {
 		[[repository windowController] showMessageSheet:@"No changes to commit" infoText:@"You must first stage some changes before committing"];
 		return;