diff --git a/ngraph/core/reference/include/ngraph/runtime/reference/convert.hpp b/ngraph/core/reference/include/ngraph/runtime/reference/convert.hpp
index 43bc8da26c9..a5c0ec589d0 100644
--- a/ngraph/core/reference/include/ngraph/runtime/reference/convert.hpp
+++ b/ngraph/core/reference/include/ngraph/runtime/reference/convert.hpp
@@ -19,8 +19,8 @@ namespace ngraph
             {
                 inline void set_u1(uint8_t* buf, size_t idx, uint8_t val)
                 {
-                    const int byte_idx = idx / 8;
-                    const int bit_idx = 7 - (idx % 8);
+                    const size_t byte_idx = idx / 8;
+                    const uint8_t bit_idx = 7 - (idx % 8);
                     if (val)
                     {
                         buf[byte_idx] |= (1 << bit_idx);
@@ -33,38 +33,38 @@ namespace ngraph
 
                 inline uint8_t get_u1(const uint8_t* buf, size_t idx)
                 {
-                    const int byte_idx = idx / 8;
-                    const int bit_idx = 7 - (idx % 8);
+                    const size_t byte_idx = idx / 8;
+                    const uint8_t bit_idx = 7 - (idx % 8);
                     return (buf[byte_idx] & (1 << bit_idx)) ? 1 : 0;
                 }
 
                 inline void set_u4(uint8_t* buf, size_t idx, uint8_t val)
                 {
-                    const int byte_idx = idx / 2;
-                    const int bit_shift = 4 * (++idx % 2);
+                    const size_t byte_idx = idx / 2;
+                    const uint8_t bit_shift = 4 * (++idx % 2);
                     buf[byte_idx] &= ~(0xF << bit_shift); // half byte zeroed
                     buf[byte_idx] |= (val << bit_shift);  // set 1's
                 }
 
                 inline uint8_t get_u4(const uint8_t* buf, size_t idx)
                 {
-                    const int byte_idx = idx / 2;
-                    const int bit_shift = 4 * (++idx % 2);
+                    const size_t byte_idx = idx / 2;
+                    const uint8_t bit_shift = 4 * (++idx % 2);
                     return (buf[byte_idx] >> bit_shift) & 0xF;
                 }
 
                 inline void set_i4(uint8_t* buf, size_t idx, int8_t val)
                 {
-                    const int byte_idx = idx / 2;
-                    const int bit_shift = 4 * (++idx % 2);
+                    const size_t byte_idx = idx / 2;
+                    const uint8_t bit_shift = 4 * (++idx % 2);
                     buf[byte_idx] &= ~(0xF << bit_shift); // half byte zeroed
                     buf[byte_idx] |= (val << bit_shift);  // set 1's
                 }
 
                 inline int8_t get_i4(const uint8_t* buf, size_t idx)
                 {
-                    const int byte_idx = idx / 2;
-                    const int bit_shift = 4 * (++idx % 2);
+                    const size_t byte_idx = idx / 2;
+                    const uint8_t bit_shift = 4 * (++idx % 2);
                     uint8_t val = (buf[byte_idx] >> bit_shift) & 0xF;
                     if (val & 0x08)
                     { // negative number