diff --git a/src/Sprites.cpp b/src/Sprites.cpp
index d4b833e..183ded0 100644
--- a/src/Sprites.cpp
+++ b/src/Sprites.cpp
@@ -69,7 +69,7 @@ void Sprites::draw(int16_t x, int16_t y,
 
 void Sprites::drawBitmap(int16_t x, int16_t y,
                          const uint8_t *bitmap, const uint8_t *mask,
-                         int8_t w, int8_t h, uint8_t draw_mode)
+                         uint8_t w, uint8_t h, uint8_t draw_mode)
 {
   // no need to draw at all of we're offscreen
   if (x + w <= 0 || x > WIDTH - 1 || y + h <= 0 || y > HEIGHT - 1)
diff --git a/src/Sprites.h b/src/Sprites.h
index 58a738b..f652ad1 100644
--- a/src/Sprites.h
+++ b/src/Sprites.h
@@ -224,7 +224,7 @@ class Sprites
     // (Not officially part of the API)
     void drawBitmap(int16_t x, int16_t y,
                     const uint8_t *bitmap, const uint8_t *mask,
-                    int8_t w, int8_t h, uint8_t draw_mode);
+                    uint8_t w, uint8_t h, uint8_t draw_mode);
 };
 
 #endif