From b0b43f6d8ed14d5884ba56e2c12fbcb6ad0e609a Mon Sep 17 00:00:00 2001
From: Thomas Fussell <thomas.fussell@gmail.com>
Date: Fri, 8 Sep 2017 13:57:29 -0400
Subject: [PATCH] cast character correctly for std::toupper

---
 source/cell/cell_reference.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/cell/cell_reference.cpp b/source/cell/cell_reference.cpp
index 15736fdd..159af274 100644
--- a/source/cell/cell_reference.cpp
+++ b/source/cell/cell_reference.cpp
@@ -122,7 +122,7 @@ std::pair<std::string, row_t> cell_reference::split_reference(
 
     for (auto character : reference_string)
     {
-        char upper = std::toupper(character);
+        auto upper = static_cast<char>(std::toupper(static_cast<std::uint8_t>(character)));
 
         if (std::isalpha(character))
         {