diff --git a/src/calibre/gui2/pictureflow/pictureflow.cpp b/src/calibre/gui2/pictureflow/pictureflow.cpp
index 5eb44c2a4f..df2231bd0d 100644
--- a/src/calibre/gui2/pictureflow/pictureflow.cpp
+++ b/src/calibre/gui2/pictureflow/pictureflow.cpp
@@ -870,11 +870,6 @@ static inline uint BYTE_MUL_RGB16(uint x, uint a) {
     return t;
 }
 
-static inline uint BYTE_MUL_RGB16_32(uint x, uint a) {
-    uint t = (((x & 0xf81f07e0) >> 5)*a) & 0xf81f07e0;
-    t |= (((x & 0x07e0f81f)*a) >> 5) & 0x07e0f81f;
-    return t;
-}
 
 QRect PictureFlowPrivate::renderCenterSlide(const SlideInfo &slide) {
   QImage* src = surface(slide.slideIndex);