diff --git a/include/git2/thread-utils.h b/include/git2/thread-utils.h
index fb8644b93..e26876bea 100644
--- a/include/git2/thread-utils.h
+++ b/include/git2/thread-utils.h
@@ -35,6 +35,7 @@
 
 #if defined(__APPLE__) && defined(__MACH__)
 # undef GIT_TLS
+# define GIT_TLS
 
 #elif defined(__GNUC__) || \
       defined(__SUNPRO_C) || \
diff --git a/src/common.h b/src/common.h
index 5ad878e26..b3f5253a9 100644
--- a/src/common.h
+++ b/src/common.h
@@ -56,4 +56,6 @@ typedef SSIZE_T ssize_t;
 
 #define GIT_PATH_MAX 4096
 
+extern int git__error(int error, const char *, ...) GIT_FORMAT_PRINTF(2, 3);
+
 #endif /* INCLUDE_common_h__ */
diff --git a/src/errors.c b/src/errors.c
index c3a495cc9..b0c1c1519 100644
--- a/src/errors.c
+++ b/src/errors.c
@@ -1,6 +1,33 @@
+/*
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2,
+ * as published by the Free Software Foundation.
+ *
+ * In addition to the permissions in the GNU General Public License,
+ * the authors give you unlimited permission to link the compiled
+ * version of this file into combinations with other programs,
+ * and to distribute those combinations without any restriction
+ * coming from the use of this file.  (The General Public License
+ * restrictions do apply in other respects; for example, they cover
+ * modification of the file, and distribution when not linked into
+ * a combined executable.)
+ *
+ * This file is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
 #include "common.h"
+#include "git2/thread-utils.h" /* for GIT_TLS */
 #include "thread-utils.h" /* for GIT_TLS */
 
+#include <stdarg.h>
+
 static struct {
 	int num;
 	const char *str;
@@ -46,3 +73,16 @@ const char *git_strerror(int num)
 
 	return "Unknown error";
 }
+
+static GIT_TLS char g_last_error[1024];
+
+int git__error(int error, const char *msg, ...)
+{
+	va_list va;
+
+	va_start(va, msg);
+	vsnprintf(g_last_error, sizeof(g_last_error), msg, va);
+	va_end(va);
+
+	return error;
+}