thodg/libgit2

diff --git a/src/errors.c b/src/errors.c
index 3616fdb..880163f 100644
--- a/src/errors.c
+++ b/src/errors.c
@@ -26,7 +26,8 @@ static struct {
 	{GIT_ETOONESTEDSYMREF, "The specified symbolic reference is too deeply nested"},
 	{GIT_EPACKEDREFSCORRUPTED, "The pack-refs file is either corrupted of its format is not currently supported"},
 	{GIT_EINVALIDPATH, "The path is invalid" },
-	{GIT_EREVWALKOVER, "The revision walker is empty; there are no more commits left to iterate"}
+	{GIT_EREVWALKOVER, "The revision walker is empty; there are no more commits left to iterate"},
+	{GIT_EINVALIDREFSTATE, "The state of the reference is not valid"}
 };
 
 const char *git_strerror(int num)
diff --git a/src/git2/common.h b/src/git2/common.h
index 3500a2b..34efe80 100644
--- a/src/git2/common.h
+++ b/src/git2/common.h
@@ -154,6 +154,9 @@
 /** The revision walker is empty; there are no more commits left to iterate */
 #define GIT_EREVWALKOVER (GIT_ERROR - 20)
 
+/** The state of the reference is not valid */
+#define GIT_EINVALIDREFSTATE (GIT_ERROR - 21)
+
 GIT_BEGIN_DECL
 /** @} */
 GIT_END_DECL