diff --git a/src/mesa/main/blend.c b/src/mesa/main/blend.c
index e8c211ede61..d069943917b 100644
--- a/src/mesa/main/blend.c
+++ b/src/mesa/main/blend.c
@@ -1032,7 +1032,7 @@ _mesa_ColorMaski(GLuint buf, GLboolean red, GLboolean green,
 
    FLUSH_VERTICES(ctx, 0, GL_COLOR_BUFFER_BIT);
    ctx->NewDriverState |= ST_NEW_BLEND;
-   ctx->Color.ColorMask &= ~(0xf << (4 * buf));
+   ctx->Color.ColorMask &= ~(0xfu << (4 * buf));
    ctx->Color.ColorMask |= mask << (4 * buf);
    _mesa_update_allow_draw_out_of_order(ctx);
 }