diff --git a/release/c/wuffs-unsupported-snapshot.c b/release/c/wuffs-unsupported-snapshot.c
index 69bdd08..1638611 100644
--- a/release/c/wuffs-unsupported-snapshot.c
+++ b/release/c/wuffs-unsupported-snapshot.c
@@ -13444,7 +13444,7 @@
           } else {
             v_src[0] = 255;
           }
-          v_c <<= 1;
+          v_c = ((uint8_t)(((((uint32_t)(v_c)) << 1) & 255)));
           wuffs_base__pixel_swizzler__swizzle_interleaved(
               &self->private_impl.f_swizzler, v_dst,
               wuffs_base__utility__empty_slice_u8(),
diff --git a/std/wbmp/decode_wbmp.wuffs b/std/wbmp/decode_wbmp.wuffs
index 120d0ae..fd9f129 100644
--- a/std/wbmp/decode_wbmp.wuffs
+++ b/std/wbmp/decode_wbmp.wuffs
@@ -176,7 +176,12 @@
 				} else {
 					src[0] = 0xFF
 				}
-				c ~mod<<= 1
+				// TODO: this should just be "c ~mod<<= 1", but that generates:
+				//
+				// error: conversion to ‘uint8_t {aka unsigned char}’ from
+				// ‘int’ may alter its value [-Werror=conversion]
+				//     v_c <<= 1;
+				c = (((c as base.u32) << 1) & 0xFF) as base.u8
 
 				this.swizzler.swizzle_interleaved!(
 					dst: dst, dst_palette: this.util.empty_slice_u8(), src: src[..])