diff --git a/libswscale/swscale.c b/libswscale/swscale.c
index 689233c07b..83607d2b77 100644
--- a/libswscale/swscale.c
+++ b/libswscale/swscale.c
@@ -1849,6 +1849,8 @@ int sws_scale(SwsContext *c, const uint8_t* const src[], const int srcStride[],
                 r= (i>>3    )*255;
                 g= ((i>>1)&3)*85;
                 b= (i&1     )*255;
+            } else if(c->srcFormat == PIX_FMT_GRAY8) {
+                r = g = b = i;
             } else {
                 assert(c->srcFormat == PIX_FMT_BGR4_BYTE);
                 b= (i>>3    )*255;