diff --git a/src/cuda_gpupreagg.cu b/src/cuda_gpupreagg.cu
index 0a0cd6262..65c7935d0 100644
--- a/src/cuda_gpupreagg.cu
+++ b/src/cuda_gpupreagg.cu
@@ -576,7 +576,6 @@ __update_nogroups__psum_int(kern_context *kcxt,
 		kagg_state__psum_int_packed *r =
 			(kagg_state__psum_int_packed *)buffer;
 
-		assert(ival >= 0);
 		pgstrom_stair_sum_int64(ival, &sum);
 		if (get_local_id() == 0)
 		{
diff --git a/src/cuda_gpuscan.cu b/src/cuda_gpuscan.cu
index e8406eac1..433db6b61 100644
--- a/src/cuda_gpuscan.cu
+++ b/src/cuda_gpuscan.cu
@@ -95,7 +95,6 @@ pgstrom_stair_sum_binary(bool predicate, uint32_t *p_total_count)
 																		\
 		assert(__activemask() == ~0U);									\
 		warp_sum = __stair_sum_warp_common(value);						\
-		assert(warp_sum >= value);										\
 		if (LaneId() == warpSize - 1)									\
 			__stair_sum_buffer.FIELD[warp_id] = warp_sum;				\
 		__syncthreads();												\