diff --git a/Adafruit_GFX.cpp b/Adafruit_GFX.cpp
index 8a31207b..cd7d2ae9 100755
--- a/Adafruit_GFX.cpp
+++ b/Adafruit_GFX.cpp
@@ -1364,8 +1364,9 @@ void Adafruit_GFX::setFont(const GFXfont *f) {
     @param    maxy  Maximum clipping value for Y
 */
 /**************************************************************************/
-void Adafruit_GFX::charBounds(char c, int16_t *x, int16_t *y, int16_t *minx,
-                              int16_t *miny, int16_t *maxx, int16_t *maxy) {
+void Adafruit_GFX::charBounds(unsigned char c, int16_t *x, int16_t *y,
+                              int16_t *minx, int16_t *miny, int16_t *maxx,
+                              int16_t *maxy) {
 
   if (gfxFont) {
 
diff --git a/Adafruit_GFX.h b/Adafruit_GFX.h
index 1bbac477..e81dd74d 100644
--- a/Adafruit_GFX.h
+++ b/Adafruit_GFX.h
@@ -227,8 +227,8 @@ class Adafruit_GFX : public Print {
   int16_t getCursorY(void) const { return cursor_y; };
 
 protected:
-  void charBounds(char c, int16_t *x, int16_t *y, int16_t *minx, int16_t *miny,
-                  int16_t *maxx, int16_t *maxy);
+  void charBounds(unsigned char c, int16_t *x, int16_t *y, int16_t *minx,
+                  int16_t *miny, int16_t *maxx, int16_t *maxy);
   int16_t WIDTH;        ///< This is the 'raw' display width - never changes
   int16_t HEIGHT;       ///< This is the 'raw' display height - never changes
   int16_t _width;       ///< Display width as modified by current rotation