diff --git a/src/gallium/drivers/llvmpipe/lp_state_fs.c b/src/gallium/drivers/llvmpipe/lp_state_fs.c
index 4bfccd83e17..4fe5e88dcfe 100644
--- a/src/gallium/drivers/llvmpipe/lp_state_fs.c
+++ b/src/gallium/drivers/llvmpipe/lp_state_fs.c
@@ -181,6 +181,7 @@ lp_mem_type_from_format_desc(const struct util_format_description *format_desc,
    }
 
    int chan = util_format_get_first_non_void_channel(format_desc->format);
+   assert(chan >= 0);
 
    memset(type, 0, sizeof(struct lp_type));
    type->floating = format_desc->channel[chan].type == UTIL_FORMAT_TYPE_FLOAT;
@@ -1783,7 +1784,8 @@ lp_blend_type_from_format_desc(const struct util_format_description *format_desc
       return;
    }
 
-   const int chan = util_format_get_first_non_void_channel(format_desc->format);
+   int chan = util_format_get_first_non_void_channel(format_desc->format);
+   assert(chan >= 0);
 
    memset(type, 0, sizeof(struct lp_type));
    type->floating = format_desc->channel[chan].type == UTIL_FORMAT_TYPE_FLOAT;