diff --git a/libs/vkd3d-shader/dxil.c b/libs/vkd3d-shader/dxil.c
index ca150831d..eda03ab71 100644
--- a/libs/vkd3d-shader/dxil.c
+++ b/libs/vkd3d-shader/dxil.c
@@ -6857,6 +6857,10 @@ static enum vkd3d_shader_opcode sm6_map_cast_op(uint64_t code, const struct sm6_
                 VKD3D_ASSERT(from->u.width == 1 || to->u.width == 64);
                 is_valid = from_int && to_int;
             }
+            else
+            {
+                is_valid = false;
+            }
             break;
         case CAST_FPTOUI:
             op = VKD3DSIH_FTOU;