diff --git a/lib/sanitizer_common/sanitizer_stack_store.cpp b/lib/sanitizer_common/sanitizer_stack_store.cpp
index 19f2c17..8f1f952 100644
--- a/lib/sanitizer_common/sanitizer_stack_store.cpp
+++ b/lib/sanitizer_common/sanitizer_stack_store.cpp
@@ -37,16 +37,23 @@
   if (!trace.size && !trace.tag)
     return 0;
   StackTraceHeader h(trace);
-  uptr *stack_trace = Alloc(h.size + 1);
+  uptr idx;
+  uptr *stack_trace = Alloc(h.size + 1, &idx);
   *stack_trace = h.ToUptr();
   internal_memcpy(stack_trace + 1, trace.trace, h.size * sizeof(uptr));
-  return reinterpret_cast<StackStore::Id>(stack_trace);
+  return OffsetToId(idx);
 }
 
 StackTrace StackStore::Load(Id id) const {
   if (!id)
     return {};
-  const uptr *stack_trace = reinterpret_cast<const uptr *>(id);
+  uptr idx = IdToOffset(id);
+  uptr block_idx = GetBlockIdx(idx);
+  CHECK_LT(block_idx, ARRAY_SIZE(blocks_));
+  uptr *stack_trace = blocks_[block_idx].Get();
+  if (!stack_trace)
+    return {};
+  stack_trace += GetInBlockIdx(idx);
   StackTraceHeader h(*stack_trace);
   return StackTrace(stack_trace + 1, h.size, h.tag);
 }
@@ -57,7 +64,7 @@
          sizeof(*this);
 }
 
-uptr *StackStore::Alloc(uptr count) {
+uptr *StackStore::Alloc(uptr count, uptr *idx) {
   for (;;) {
     // Optimisic lock-free allocation, essentially try to bump the
     // total_frames_.
@@ -66,6 +73,7 @@
     if (LIKELY(block_idx == GetBlockIdx(start + count - 1))) {
       // Fits into the a single block.
       CHECK_LT(block_idx, ARRAY_SIZE(blocks_));
+      *idx = start;
       return blocks_[block_idx].GetOrCreate() + GetInBlockIdx(start);
     }
 
diff --git a/lib/sanitizer_common/sanitizer_stack_store.h b/lib/sanitizer_common/sanitizer_stack_store.h
index 389bb48..f1e99d1 100644
--- a/lib/sanitizer_common/sanitizer_stack_store.h
+++ b/lib/sanitizer_common/sanitizer_stack_store.h
@@ -25,7 +25,9 @@
  public:
   constexpr StackStore() = default;
 
-  using Id = uptr;
+  using Id = u32;  // Enough for 2^32 * sizeof(uptr) bytes of traces.
+  static_assert(u64(kBlockCount) * kBlockSizeFrames == 1ull << (sizeof(Id) * 8),
+                "");
 
   Id Store(const StackTrace &trace);
   StackTrace Load(Id id) const;
@@ -42,7 +44,19 @@
     return frame_idx % kBlockSizeFrames;
   }
 
-  uptr *Alloc(uptr count);
+  static constexpr uptr IdToOffset(Id id) {
+    CHECK_NE(id, 0);
+    return id - 1;  // Avoid zero as id.
+  }
+
+  static constexpr uptr OffsetToId(Id id) {
+    // This makes UINT32_MAX to 0 and it will be retrived as and empty stack.
+    // But this is not a problem as we will not be able to store anything after
+    // that anyway.
+    return id + 1;  // Avoid zero as id.
+  }
+
+  uptr *Alloc(uptr count, uptr *idx);
 
   // Total number of allocated frames.
   atomic_uintptr_t total_frames_ = {};
@@ -53,9 +67,9 @@
     StaticSpinMutex mtx_;  // Protects alloc of new blocks.
 
     uptr *Create();
-    uptr *Get() const;
 
    public:
+    uptr *Get() const;
     uptr *GetOrCreate();
     void TestOnlyUnmap();
   };