diff --git a/PBGitHistoryView.xib b/PBGitHistoryView.xib
index 2a02912..0dd3331 100644
--- a/PBGitHistoryView.xib
+++ b/PBGitHistoryView.xib
@@ -8,7 +8,7 @@
 		<string key="IBDocument.HIToolboxVersion">353.00</string>
 		<object class="NSMutableArray" key="IBDocument.EditedObjectIDs">
 			<bool key="EncodedWithXMLCoder">YES</bool>
-			<integer value="236"/>
+			<integer value="237"/>
 			<integer value="27"/>
 		</object>
 		<object class="NSArray" key="IBDocument.PluginDependencies">
@@ -1117,6 +1117,25 @@
 								<int key="NSPeriodicInterval">25</int>
 							</object>
 						</object>
+						<object class="NSTextField" id="27300806">
+							<reference key="NSNextResponder" ref="562356688"/>
+							<int key="NSvFlags">268</int>
+							<string key="NSFrame">{{251, 62}, {85, 17}}</string>
+							<reference key="NSSuperview" ref="562356688"/>
+							<bool key="NSEnabled">YES</bool>
+							<object class="NSTextFieldCell" key="NSCell" id="217429948">
+								<int key="NSCellFlags">68288064</int>
+								<int key="NSCellFlags2">272630784</int>
+								<string key="NSContents">Invalid name</string>
+								<reference key="NSSupport" ref="924107556"/>
+								<reference key="NSControlView" ref="27300806"/>
+								<reference key="NSBackgroundColor" ref="457244339"/>
+								<object class="NSColor" key="NSTextColor">
+									<int key="NSColorSpace">1</int>
+									<bytes key="NSRGB">MSAwIDAAA</bytes>
+								</object>
+							</object>
+						</object>
 					</object>
 					<string key="NSFrameSize">{346, 133}</string>
 					<reference key="NSSuperview"/>
@@ -2075,6 +2094,14 @@
 					</object>
 					<int key="connectionID">271</int>
 				</object>
+				<object class="IBConnectionRecord">
+					<object class="IBOutletConnection" key="connection">
+						<string key="label">errorMessage</string>
+						<reference key="source" ref="892732705"/>
+						<reference key="destination" ref="27300806"/>
+					</object>
+					<int key="connectionID">274</int>
+				</object>
 			</object>
 			<object class="IBMutableOrderedSet" key="objectRecords">
 				<object class="NSArray" key="orderedObjects">
@@ -2389,6 +2416,7 @@
 							<reference ref="383988892"/>
 							<reference ref="60467344"/>
 							<reference ref="657747237"/>
+							<reference ref="27300806"/>
 						</object>
 						<reference key="parent" ref="296392339"/>
 					</object>
@@ -2690,6 +2718,20 @@
 						<reference key="object" ref="496187369"/>
 						<reference key="parent" ref="604026377"/>
 					</object>
+					<object class="IBObjectRecord">
+						<int key="objectID">272</int>
+						<reference key="object" ref="27300806"/>
+						<object class="NSMutableArray" key="children">
+							<bool key="EncodedWithXMLCoder">YES</bool>
+							<reference ref="217429948"/>
+						</object>
+						<reference key="parent" ref="562356688"/>
+					</object>
+					<object class="IBObjectRecord">
+						<int key="objectID">273</int>
+						<reference key="object" ref="217429948"/>
+						<reference key="parent" ref="27300806"/>
+					</object>
 				</object>
 			</object>
 			<object class="NSMutableDictionary" key="flattenedProperties">
@@ -2767,6 +2809,8 @@
 					<string>27.IBViewIntegration.shadowOffsetHeight</string>
 					<string>27.IBViewIntegration.shadowOffsetWidth</string>
 					<string>27.ImportedFromIB2</string>
+					<string>272.IBPluginDependency</string>
+					<string>273.IBPluginDependency</string>
 					<string>28.IBPluginDependency</string>
 					<string>28.IBShouldRemoveOnLegacySave</string>
 					<string>29.IBPluginDependency</string>
@@ -2859,8 +2903,8 @@
 					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
 					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
 					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
-					<string>{{521, 623}, {346, 133}}</string>
-					<string>{{521, 623}, {346, 133}}</string>
+					<string>{{504, 581}, {346, 133}}</string>
+					<string>{{504, 581}, {346, 133}}</string>
 					<reference ref="8"/>
 					<string>{3.40282e+38, 3.40282e+38}</string>
 					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
@@ -2896,6 +2940,8 @@
 					<reference ref="8"/>
 					<reference ref="9"/>
 					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
+					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
+					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
 					<reference ref="9"/>
 					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
 					<reference ref="9"/>
@@ -2929,7 +2975,7 @@
 					</object>
 					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
 					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
-					<string>{{312, 79}, {852, 432}}</string>
+					<string>{{189, 79}, {852, 432}}</string>
 					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
 					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
 					<string>com.apple.InterfaceBuilder.CocoaPlugin</string>
@@ -2964,7 +3010,7 @@
 				</object>
 			</object>
 			<nil key="sourceID"/>
-			<int key="maxID">271</int>
+			<int key="maxID">274</int>
 		</object>
 		<object class="IBClassDescriber" key="IBDocument.Classes">
 			<object class="NSMutableArray" key="referencedPartialClassDescriptions">
@@ -3120,6 +3166,7 @@
 							<string>branchPopUp</string>
 							<string>commitController</string>
 							<string>commitList</string>
+							<string>errorMessage</string>
 							<string>historyController</string>
 							<string>newBranchName</string>
 							<string>newBranchSheet</string>
@@ -3129,6 +3176,7 @@
 							<string>NSPopUpButton</string>
 							<string>NSArrayController</string>
 							<string>PBCommitList</string>
+							<string>NSTextField</string>
 							<string>PBGitHistoryController</string>
 							<string>NSTextField</string>
 							<string>NSWindow</string>
diff --git a/PBRefController.h b/PBRefController.h
index 4ec8990..0706fc5 100644
--- a/PBRefController.h
+++ b/PBRefController.h
@@ -20,6 +20,7 @@
 
 	IBOutlet NSWindow *newBranchSheet;
 	IBOutlet NSTextField *newBranchName;
+	IBOutlet NSTextField *errorMessage;
 
 	IBOutlet NSPopUpButton *branchPopUp;
 }
diff --git a/PBRefController.m b/PBRefController.m
index ccd5abd..b498386 100644
--- a/PBRefController.m
+++ b/PBRefController.m
@@ -160,6 +160,7 @@
 # pragma mark Add ref methods
 -(void)addRef:(id)sender
 {
+	[errorMessage setStringValue:@""];
 	[NSApp beginSheet:newBranchSheet
 	   modalForWindow:[[historyController view] window]
 		modalDelegate:NULL
@@ -170,20 +171,28 @@
 -(void)saveSheet:(id) sender
 {
 	NSString *branchName = [@"refs/heads/" stringByAppendingString:[newBranchName stringValue]];
-	[self closeSheet:sender];
 	
 	if ([[commitController selectedObjects] count] == 0)
 		return;
-	
+
 	PBGitCommit *commit = [[commitController selectedObjects] objectAtIndex:0];
+
 	int retValue = 1;
-	[historyController.repository outputForArguments:[NSArray arrayWithObjects:@"update-ref", @"-mCreate branch from GitX", branchName, [commit realSha], NULL] retValue:&retValue];
-	if (retValue)
-	{
-		NSLog(@"Creating ref failed!");
+	[historyController.repository outputForArguments:[NSArray arrayWithObjects:@"check-ref-format", branchName, nil] retValue:&retValue];
+	if (retValue != 0) {
+		[errorMessage setStringValue:@"Invalid name"];
 		return;
 	}
 
+	retValue = 1;
+	[historyController.repository outputForArguments:[NSArray arrayWithObjects:@"update-ref", @"-mCreate branch from GitX", branchName, [commit realSha], @"0000000000000000000000000000000000000000", NULL] retValue:&retValue];
+	if (retValue)
+	{
+		[errorMessage setStringValue:@"Branch exists"];
+		return;
+	}
+
+	[self closeSheet:sender];
 	[commit addRef:[PBGitRef refFromString:branchName]];
 	[commitController rearrangeObjects];
 }