diff --git a/PBGitXErrors.h b/PBGitXErrors.h
index 3be78a2..fca620e 100644
--- a/PBGitXErrors.h
+++ b/PBGitXErrors.h
@@ -26,6 +26,9 @@ extern NSString * const PBGitRepositoryErrorDomain;
 extern NSString * const PBInvalidBranchErrorMessage;
 extern NSString * const PBMissingRemoteErrorMessage;
 
-extern const NSInteger PBFileReadingUnsupportedErrorCode;   /* @"Reading files is not supported." */
-extern const NSInteger PBNotAGitRepositoryErrorCode;        /* @"%@ does not appear to be a git repository." */
-extern const NSInteger PBGitBinaryNotFoundErrorCode;
\ No newline at end of file
+extern const NSInteger PBFileReadingUnsupportedErrorCode;           /* @"Reading files is not supported." */
+extern const NSInteger PBNotAGitRepositoryErrorCode;                /* @"%@ does not appear to be a git repository." */
+extern const NSInteger PBGitBinaryNotFoundErrorCode;
+extern const NSInteger PBNotAValidRefFormatErrorCode;               /* happens when check-ref-format in PBGitRepository -checkRefFormat returns NO */
+// extern const NSInteger PBCLINilValueForArgumentsCode;               /* PBCLIProxy -openRepository:arguments:error: is passed nil for arguments */
+// extern const NSInteger PBCLINilValueForRepositoryPathErrorCode;     /* PBCLIProxy -openRepository:arguments:error: is passed nil for repositoryPath */
\ No newline at end of file
diff --git a/PBGitXErrors.m b/PBGitXErrors.m
index e86f5ff..8c9a45c 100644
--- a/PBGitXErrors.m
+++ b/PBGitXErrors.m
@@ -28,6 +28,9 @@ NSString * const PBInvalidBranchErrorMessage  = @"Please select a local branch f
 
 NSString * const PBMissingRemoteErrorMessage  = @"This branch does not appear to have a remote tracking branch associated in its config file section.";
 
-const NSInteger PBNotAGitRepositoryErrorCode        = 1;
-const NSInteger PBFileReadingUnsupportedErrorCode   = 2;
-const NSInteger PBGitBinaryNotFoundErrorCode        = 3;
\ No newline at end of file
+const NSInteger PBNotAGitRepositoryErrorCode            = 1;
+const NSInteger PBFileReadingUnsupportedErrorCode       = 2;
+const NSInteger PBGitBinaryNotFoundErrorCode            = 3;
+const NSInteger PBNotAValidRefFormatErrorCode           = 4;
+// const NSInteger PBCLINilValueForArgumentsCode           = 5;
+// const NSInteger PBCLINilValueForRepositoryPathErrorCode = 6;