diff --git a/src/util/src/tcompression.c b/src/util/src/tcompression.c
index 1ac42377fb62c9f9da1186d068da6ce603a77eea..0f0c7bed347fce36ea8054ce523619998a1f6327 100644
--- a/src/util/src/tcompression.c
+++ b/src/util/src/tcompression.c
@@ -355,16 +355,16 @@ int tsCompressINTImp(const char *const input, const int nelements, char *const o
         tmp_bit = (LONG_BYTES * BITS_PER_BYTE) - BUILDIN_CLZL(zigzag_value);
       }
 
-      if (elems + 1 <= selector_to_elems[selector] && elems + 1 <= selector_to_elems[bit_to_selector[tmp_bit]]) {
+      if (elems + 1 <= selector_to_elems[(int)selector] && elems + 1 <= selector_to_elems[(int)(bit_to_selector[(int)tmp_bit])]) {
         // If can hold another one.
-        selector = selector > bit_to_selector[tmp_bit] ? selector : bit_to_selector[tmp_bit];
+        selector = selector > bit_to_selector[(int)tmp_bit] ? selector : bit_to_selector[(int)tmp_bit];
         elems++;
-        bit = bit_per_integer[selector];
+        bit = bit_per_integer[(int)selector];
       } else {
         // if cannot hold another one.
-        while (elems < selector_to_elems[selector]) selector++;
-        elems = selector_to_elems[selector];
-        bit = bit_per_integer[selector];
+        while (elems < selector_to_elems[(int)selector]) selector++;
+        elems = selector_to_elems[(int)selector];
+        bit = bit_per_integer[(int)selector];
         break;
       }
       prev_value_tmp = curr_value;
@@ -455,8 +455,8 @@ int tsDecompressINTImp(const char *const input, const int nelements, char *const
     memcpy(&w, ip, LONG_BYTES);
 
     char selector = (char)(w & INT64MASK(4));  // selector = 4
-    char bit = bit_per_integer[selector];      // bit = 3
-    int  elems = selector_to_elems[selector];
+    char bit = bit_per_integer[(int)selector];      // bit = 3
+    int  elems = selector_to_elems[(int)selector];
 
     for (int i = 0; i < elems; i++) {
       uint64_t zigzag_value;
diff --git a/src/util/src/ttokenizer.c b/src/util/src/ttokenizer.c
index f402963049a71fd8d8b7329db84a99520751e775..516f02fc20d84086d3e1f7a87276db5835a45d39 100644
--- a/src/util/src/ttokenizer.c
+++ b/src/util/src/ttokenizer.c
@@ -510,7 +510,7 @@ uint32_t tSQLGetToken(char* z, uint32_t* tokenType) {
       if ((z[i] == 'a' || z[i] == 's' || z[i] == 'm' || z[i] == 'h' || z[i] == 'd' || z[i] == 'n' || z[i] == 'y' ||
           z[i] == 'w' || z[i] == 'A' || z[i] == 'S' || z[i] == 'M' || z[i] == 'H' || z[i] == 'D' || z[i] == 'N' ||
           z[i] == 'Y' || z[i] == 'W') &&
-          (isIdChar[z[i + 1]] == 0)) {
+          (isIdChar[(int)(z[i + 1])] == 0)) {
         *tokenType = TK_VARIABLE;
         i += 1;
         return i;
@@ -551,7 +551,7 @@ uint32_t tSQLGetToken(char* z, uint32_t* tokenType) {
     case 't':
     case 'F':
     case 'f': {
-      for (i = 1; ((z[i] & 0x80) == 0) && isIdChar[z[i]]; i++) {
+      for (i = 1; ((z[i] & 0x80) == 0) && isIdChar[(int)(z[i])]; i++) {
       }
 
       if ((i == 4 && strncasecmp(z, "true", 4) == 0) || (i == 5 && strncasecmp(z, "false", 5) == 0)) {
@@ -560,10 +560,10 @@ uint32_t tSQLGetToken(char* z, uint32_t* tokenType) {
       }
     }
     default: {
-      if (((*z & 0x80) != 0) || !isIdChar[*z]) {
+      if (((*z & 0x80) != 0) || !isIdChar[(int)(*z)]) {
         break;
       }
-      for (i = 1; ((z[i] & 0x80) == 0) && isIdChar[z[i]]; i++) {
+      for (i = 1; ((z[i] & 0x80) == 0) && isIdChar[(int)(z[i])]; i++) {
       }
       *tokenType = tSQLKeywordCode(z, i);
       return i;