diff --git a/render/render.c b/render/render.c
index b2c25ccf..84b9381d 100644
--- a/render/render.c
+++ b/render/render.c
@@ -375,7 +375,7 @@ void RrMinsize(RrAppearance *a, gint *w, gint *h)
 static void reverse_bits(gchar *c, gint n)
 {
     gint i;
-    for (i = 0; i < n; i++, *c++)
+    for (i = 0; i < n; i++, c++)
         *c = (((*c * 0x0802UL & 0x22110UL) |
                (*c * 0x8020UL & 0x88440UL)) * 0x10101UL) >> 16;
 }