diff --git a/mozilla/modules/libimg/png/pngmem.c b/mozilla/modules/libimg/png/pngmem.c
index 0aeab68ef9d..ca874c72492 100644
--- a/mozilla/modules/libimg/png/pngmem.c
+++ b/mozilla/modules/libimg/png/pngmem.c
@@ -130,7 +130,7 @@ png_voidp
 png_malloc_default(png_structp png_ptr, png_uint_32 size)
 {
    png_voidp ret;
-#endif PNG_USER_MEM_SUPPORTED
+#endif /* PNG_USER_MEM_SUPPORTED */
 
 #ifdef PNG_MAX_MALLOC_64K
    if (size > (png_uint_32)65536L)