diff --git a/include/boost/sort/pdqsort/pdqsort.hpp b/include/boost/sort/pdqsort/pdqsort.hpp
index 8352e39..fd447ce 100644
--- a/include/boost/sort/pdqsort/pdqsort.hpp
+++ b/include/boost/sort/pdqsort/pdqsort.hpp
@@ -232,7 +232,7 @@ namespace pdqsort_detail {
 
                 // Fill the offset blocks.
                 if (left_split >= block_size) {
-                    for (size_t i = 0; i < block_size;) {
+                    for (unsigned char i = 0; i < static_cast<unsigned char>(block_size);) {
                         offsets_l[num_l] = i++; num_l += !comp(*first, pivot); ++first;
                         offsets_l[num_l] = i++; num_l += !comp(*first, pivot); ++first;
                         offsets_l[num_l] = i++; num_l += !comp(*first, pivot); ++first;
@@ -243,13 +243,13 @@ namespace pdqsort_detail {
                         offsets_l[num_l] = i++; num_l += !comp(*first, pivot); ++first;
                     }
                 } else {
-                    for (size_t i = 0; i < left_split;) {
+                    for (unsigned char i = 0; i < static_cast<unsigned char>(left_split);) {
                         offsets_l[num_l] = i++; num_l += !comp(*first, pivot); ++first;
                     }
                 }
 
                 if (right_split >= block_size) {
-                    for (size_t i = 0; i < block_size;) {
+                    for (unsigned char i = 0; i < static_cast<unsigned char>(block_size);) {
                         offsets_r[num_r] = ++i; num_r += comp(*--last, pivot);
                         offsets_r[num_r] = ++i; num_r += comp(*--last, pivot);
                         offsets_r[num_r] = ++i; num_r += comp(*--last, pivot);
@@ -260,7 +260,7 @@ namespace pdqsort_detail {
                         offsets_r[num_r] = ++i; num_r += comp(*--last, pivot);
                     }
                 } else {
-                    for (size_t i = 0; i < right_split;) {
+                    for (unsigned char i = 0; i < static_cast<unsigned char>(right_split);) {
                         offsets_r[num_r] = ++i; num_r += comp(*--last, pivot);
                     }
                 }