diff --git a/src/ArduinoGraphics.cpp b/src/ArduinoGraphics.cpp
index 3590eec..b47c2b5 100644
--- a/src/ArduinoGraphics.cpp
+++ b/src/ArduinoGraphics.cpp
@@ -238,7 +238,7 @@ void ArduinoGraphics::text(const char* str, int x, int y)
   }
 
   while (*str) {
-    int c = *str++;
+    uint8_t const c = (uint8_t)*str++;
 
     if (c == '\n') {
       y += _font->height;