diff --git a/lib/libc/core/errno/errno.c b/lib/libc/core/errno/errno.c
index 304bef5..51a54fb 100644
--- a/lib/libc/core/errno/errno.c
+++ b/lib/libc/core/errno/errno.c
@@ -11,7 +11,7 @@ int __attribute__((weak)) * __errno_location(void)
 #if defined(BUILD_STATIC)
 int __set_errno(int err)
 {
-	return -err;
+	return err == 0 ? 0 : -err;
 }
 #endif
 
@@ -20,7 +20,7 @@ int __set_errno(int err)
 {
 	/* TODO */
 	*__errno_location() = err;
-	return -1;
+	return err == 0 ? 0 : -1;
 }
 #endif