diff --git a/src/PicoDVI.h b/src/PicoDVI.h
index e89e108..0d84cdd 100644
--- a/src/PicoDVI.h
+++ b/src/PicoDVI.h
@@ -118,7 +118,7 @@ class DVIGFX16 : public PicoDVI, public GFXcanvas16 {
     @param   blue   Blue component, 0-255.
     @return  Nearest 16-bit RGB565 equivalent.
   */
-  uint16_t color565(uint8_t red, uint8_t green, uint8_t blue) {
+  static uint16_t color565(uint8_t red, uint8_t green, uint8_t blue) {
     return ((red & 0xF8) << 8) | ((green & 0xFC) << 3) | (blue >> 3);
   }
   /*!