diff --git a/ggml-cuda.cu b/ggml-cuda.cu
index c07b54611..f07bdc78d 100644
--- a/ggml-cuda.cu
+++ b/ggml-cuda.cu
@@ -220,7 +220,7 @@ typedef struct {
 static_assert(sizeof(block_q6_K) == sizeof(ggml_fp16_t) + 13*QK_K/16, "wrong q6_K block size/padding");
 
 #define WARP_SIZE 32
-#define MATRIX_ROW_PADDING 256 // last row of quant. matrices is a multiple of this to avoid out-of-bounds memory accesses
+#define MATRIX_ROW_PADDING 512 // last row of quant. matrices is a multiple of this to avoid out-of-bounds memory accesses
 
 #define CUDA_ADD_BLOCK_SIZE 256
 #define CUDA_MUL_BLOCK_SIZE 256
@@ -2815,8 +2815,8 @@ inline void ggml_cuda_op_mul_mat_vec(
 #endif
 
     if (use_mul_mat_vec_q) {
-        int64_t padded_row_size = ne00 + MATRIX_ROW_PADDING - 1;
-        padded_row_size -= padded_row_size % MATRIX_ROW_PADDING;
+        const int64_t padded_row_size = ne00 % MATRIX_ROW_PADDING == 0 ?
+            ne00 : ne00 - ne00 % MATRIX_ROW_PADDING + MATRIX_ROW_PADDING;
         size_t as;
         void * src1_q8_1 = ggml_cuda_pool_malloc(padded_row_size*sizeof(block_q8_1)/QK8_1, &as);
         quantize_row_q8_1_cuda(src1_ddf_i, src1_q8_1, ne00, padded_row_size, cudaStream_main);
@@ -3642,7 +3642,7 @@ void ggml_cuda_transform_tensor(void * data, struct ggml_tensor * tensor) {
         size_t size = ggml_nbytes_split(tensor, nrows_split);
         const size_t original_size = size;
 
-        // pad last row to a multiple of 256 elements to avoid out-of-bounds memory accesses
+        // pad last row to a multiple of 512 elements to avoid out-of-bounds memory accesses
         if (ne0 % MATRIX_ROW_PADDING != 0) {
             size += (MATRIX_ROW_PADDING - ne0 % MATRIX_ROW_PADDING)
                 * ggml_type_size(tensor->type)/ggml_blck_size(tensor->type);
@@ -3658,7 +3658,7 @@ void ggml_cuda_transform_tensor(void * data, struct ggml_tensor * tensor) {
         }
 
 
-        CUDA_CHECK(cudaMemcpy(buf, buf_host, size, cudaMemcpyHostToDevice));
+        CUDA_CHECK(cudaMemcpy(buf, buf_host, original_size, cudaMemcpyHostToDevice));
 
         extra->data_device[id] = buf;