diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4ccaf1d6..5dccab73 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,9 @@ Full documentation for hipCUB is available at [https://rocm.docs.amd.com/project
 * Updated `thread_load` and `thread_store` to align hipCUB with CUB.
 * All kernels now have hidden symbol visibility. All symbols now have inline namespaces that include the library version, (for example, hipcub::HIPCUB_300400_NS::symbol instead of hipcub::symbol), letting the user link multiple libraries built with different versions of hipCUB.
 
+### Resolved issues
+* Fixed an issue where `Sort(keys, compare_op, valid_items, oob_default)` in `block_merge_sort.hpp` would not fill in elements that are out of range (items after `valid_items`) with `oob_default`.
+
 ### Known issues
 
 * `BlockAdjacentDifference::FlagHeads`, `BlockAdjacentDifference::FlagTails` and `BlockAdjacentDifference::FlagHeadsAndTails` have been removed from hipCUB's CUB backend. They were already deprecated as of version 2.12.0 of hipCUB and they were removed from CCCL (CUB) as of CCCL's 2.6.0 release.
diff --git a/hipcub/include/hipcub/backend/rocprim/block/block_merge_sort.hpp b/hipcub/include/hipcub/backend/rocprim/block/block_merge_sort.hpp
index 1593062f..8d3bf048 100644
--- a/hipcub/include/hipcub/backend/rocprim/block/block_merge_sort.hpp
+++ b/hipcub/include/hipcub/backend/rocprim/block/block_merge_sort.hpp
@@ -172,7 +172,8 @@ template <typename KeyT,
           typename ValueT,
           int NUM_THREADS,
           int ITEMS_PER_THREAD,
-          typename SynchronizationPolicy>
+          typename SynchronizationPolicy,
+          bool WARP_SORT = false>
 class BlockMergeSortStrategy
 {
   static_assert(PowerOfTwo<NUM_THREADS>::VALUE,
@@ -387,7 +388,7 @@ class BlockMergeSortStrategy
       KeyT max_key = oob_default;
 
       #pragma unroll
-      for (int item = 1; item < ITEMS_PER_THREAD; ++item)
+      for (int item = WARP_SORT ? 1 : 0; item < ITEMS_PER_THREAD; ++item)
       {
         if (ITEMS_PER_THREAD * static_cast<int>(linear_tid) + item < valid_items)
         {
@@ -439,14 +440,16 @@ class BlockMergeSortStrategy
 
       int thread_idx_in_thread_group_being_merged = mask & linear_tid;
 
+      const int COMPARE_NUM = WARP_SORT ? valid_items : ITEMS_PER_THREAD * blockDim.x;
+
       int diag =
-        (::rocprim::min)(valid_items,
+        (::rocprim::min)(COMPARE_NUM,
                    ITEMS_PER_THREAD * thread_idx_in_thread_group_being_merged);
 
-      int keys1_beg = (::rocprim::min)(valid_items, start);
-      int keys1_end = (::rocprim::min)(valid_items, keys1_beg + size);
+      int keys1_beg = (::rocprim::min)(COMPARE_NUM, start);
+      int keys1_end = (::rocprim::min)(COMPARE_NUM, keys1_beg + size);
       int keys2_beg = keys1_end;
-      int keys2_end = (::rocprim::min)(valid_items, keys2_beg + size);
+      int keys2_end = (::rocprim::min)(COMPARE_NUM, keys2_beg + size);
 
       int keys1_count = keys1_end - keys1_beg;
       int keys2_count = keys2_end - keys2_beg;
diff --git a/hipcub/include/hipcub/backend/rocprim/warp/warp_merge_sort.hpp b/hipcub/include/hipcub/backend/rocprim/warp/warp_merge_sort.hpp
index 5d7a6271..136e674f 100644
--- a/hipcub/include/hipcub/backend/rocprim/warp/warp_merge_sort.hpp
+++ b/hipcub/include/hipcub/backend/rocprim/warp/warp_merge_sort.hpp
@@ -129,7 +129,8 @@ class WarpMergeSort
         ValueT,
         LOGICAL_WARP_THREADS,
         ITEMS_PER_THREAD,
-        WarpMergeSort<KeyT, ITEMS_PER_THREAD, LOGICAL_WARP_THREADS, ValueT, PTX_ARCH>>
+        WarpMergeSort<KeyT, ITEMS_PER_THREAD, LOGICAL_WARP_THREADS, ValueT, PTX_ARCH>,
+        true>
 {
 private:
   constexpr static bool IS_ARCH_WARP = LOGICAL_WARP_THREADS == HIPCUB_DEVICE_WARP_THREADS;
@@ -140,7 +141,8 @@ class WarpMergeSort
                                                          ValueT,
                                                          LOGICAL_WARP_THREADS,
                                                          ITEMS_PER_THREAD,
-                                                         WarpMergeSort>;
+                                                         WarpMergeSort,
+                                                         true>;
 
   const unsigned int warp_id;
   const uint64_t member_mask;