diff --git a/src/encoder.c b/src/encoder.c
index e781ae37..d3d7ec95 100644
--- a/src/encoder.c
+++ b/src/encoder.c
@@ -44,7 +44,7 @@
 
 double g_lambda_cost[55];
 double g_cur_lambda_cost;
-uint32_t* g_sig_last_scan[3][5];
+const uint32_t* g_sig_last_scan[3][5];
 int8_t g_convert_to_bit[LCU_WIDTH + 1];
 int8_t g_bitdepth = 8;
 
@@ -198,12 +198,17 @@ void init_tables(void)
 
   c = 2;
   for (i = 0; i < 5; i++) {
-    g_sig_last_scan[0][i] = (uint32_t*)malloc(c*c*sizeof(uint32_t));
-    g_sig_last_scan[1][i] = (uint32_t*)malloc(c*c*sizeof(uint32_t));
-    g_sig_last_scan[2][i] = (uint32_t*)malloc(c*c*sizeof(uint32_t));
+    uint32_t *sls0, *sls1, *sls2;
+    sls0 = (uint32_t*)malloc(c*c*sizeof(uint32_t));
+    sls1 = (uint32_t*)malloc(c*c*sizeof(uint32_t));
+    sls2 = (uint32_t*)malloc(c*c*sizeof(uint32_t));
 
-    init_sig_last_scan(g_sig_last_scan[0][i], g_sig_last_scan[1][i],
-                       g_sig_last_scan[2][i], c, c);
+    init_sig_last_scan(sls0, sls1, sls2, c, c);
+    
+    g_sig_last_scan[0][i] = sls0;
+    g_sig_last_scan[1][i] = sls1;
+    g_sig_last_scan[2][i] = sls2;
+    
     c <<= 1;
   }
 }
@@ -242,9 +247,9 @@ void free_tables(void)
 {
   int i;
   for (i = 0; i < 5; i++) {
-    free(g_sig_last_scan[0][i]);
-    free(g_sig_last_scan[1][i]);
-    free(g_sig_last_scan[2][i]);
+    FREE_POINTER(g_sig_last_scan[0][i]);
+    FREE_POINTER(g_sig_last_scan[1][i]);
+    FREE_POINTER(g_sig_last_scan[2][i]);
   }
 }
 encoder_control *init_encoder_control(config *cfg)
diff --git a/src/encoder.h b/src/encoder.h
index aca455e7..83ab31a9 100644
--- a/src/encoder.h
+++ b/src/encoder.h
@@ -161,7 +161,7 @@ static const uint8_t g_min_in_group[10] = {
  * First index: scan pattern 0 = diagonal, 1 = horizontal, 2 = vertical
  * Second index: (log2 - 1) size of transform block. 2x2 .. 32x32
  */
-extern uint32_t* g_sig_last_scan[3][5];
+extern const uint32_t* g_sig_last_scan[3][5];
 
 /***
   * List of indices for 4x4 coefficient groups within 8x8 transform block.
diff --git a/src/rdo.c b/src/rdo.c
index a0e74453..0dfe81fc 100644
--- a/src/rdo.c
+++ b/src/rdo.c
@@ -438,7 +438,7 @@ void  rdoq(const encoder_control * const encoder, cabac_data *cabac, coefficient
   uint32_t    c2_idx     = 0;
   int32_t     base_level;
 
-  uint32_t *scan = g_sig_last_scan[ scan_mode ][ log2_block_size - 1 ];
+  const uint32_t *scan = g_sig_last_scan[ scan_mode ][ log2_block_size - 1 ];
 
 
   uint32_t cg_num = width * height >> 4;
diff --git a/src/transform.c b/src/transform.c
index fefe9ab6..983f8f60 100644
--- a/src/transform.c
+++ b/src/transform.c
@@ -857,8 +857,8 @@ void itransform2d(int16_t *block,int16_t *coeff, int8_t block_size, int32_t mode
 void quant(const encoder_control * const encoder, int16_t *coef, int16_t *q_coef, int32_t width,
            int32_t height, uint32_t *ac_sum, int8_t type, int8_t scan_idx, int8_t block_type )
 {
-  uint32_t log2_block_size = g_convert_to_bit[ width ] + 2;
-  uint32_t *scan = g_sig_last_scan[ scan_idx ][ log2_block_size - 1 ];
+  const uint32_t log2_block_size = g_convert_to_bit[ width ] + 2;
+  const uint32_t * const scan = g_sig_last_scan[ scan_idx ][ log2_block_size - 1 ];
 
   #if ENABLE_SIGN_HIDING == 1
   int32_t delta_u[LCU_WIDTH*LCU_WIDTH>>2];
@@ -1103,7 +1103,7 @@ int scalinglist_parse(encoder_control * const encoder, FILE *fp)
   for (size_id = 0; size_id < SCALING_LIST_SIZE_NUM; size_id++) {
     uint32_t list_id;
     uint32_t size = MIN(MAX_MATRIX_COEF_NUM, (int32_t)g_scaling_list_size[size_id]);
-    //uint32_t *scan = (size_id == 0) ? g_sig_last_scan[SCAN_DIAG][1] : g_sig_last_scan_32x32;
+    //const uint32_t * const scan = (size_id == 0) ? g_sig_last_scan[SCAN_DIAG][1] : g_sig_last_scan_32x32;
 
     for (list_id = 0; list_id < g_scaling_list_num[size_id]; list_id++) {
       int found;