diff --git a/PBGitRepository.m b/PBGitRepository.m
index b3589c2..e50e342 100644
--- a/PBGitRepository.m
+++ b/PBGitRepository.m
@@ -138,8 +138,11 @@ static NSString* gitPath;
 
 - (id) initWithURL: (NSURL*) path andRevSpecifier:(PBGitRevSpecifier*) rev
 {
-	self = [self init];
 	NSURL* gitDirURL = [PBGitRepository gitDirForURL:path];
+	if (!gitDirURL)
+		return nil;
+
+	self = [self init];
 	[self setFileURL: gitDirURL];
 
 	[self setup];
diff --git a/PBRepositoryDocumentController.m b/PBRepositoryDocumentController.m
index fd30a2e..1b1cf90 100644
--- a/PBRepositoryDocumentController.m
+++ b/PBRepositoryDocumentController.m
@@ -36,6 +36,9 @@
 	id document = [self documentForURL:url];
 	if (!document) {
 		document = [[PBGitRepository alloc] initWithURL:url	andRevSpecifier:rev];
+		if (!document)
+			return nil;
+
 		[self addDocument:document];
 		[document makeWindowControllers];
 	} else {