diff --git a/lib/grnxx/map/bytes_array.cpp b/lib/grnxx/map/bytes_array.cpp
index 98a7a0b..aaaca01 100644
--- a/lib/grnxx/map/bytes_array.cpp
+++ b/lib/grnxx/map/bytes_array.cpp
@@ -110,8 +110,8 @@ void BytesArray::set(uint64_t value_id, ValueArg value) {
   *src_bytes_id = dest_bytes_id;
 }
 
-bool BytesArray::sweep(Duration lifetime) {
-  return pool_->sweep(lifetime);
+void BytesArray::sweep(Duration lifetime) {
+  pool_->sweep(lifetime);
 }
 
 BytesArray::BytesArray()
diff --git a/lib/grnxx/map/bytes_array.hpp b/lib/grnxx/map/bytes_array.hpp
index 40c7e49..125a808 100644
--- a/lib/grnxx/map/bytes_array.hpp
+++ b/lib/grnxx/map/bytes_array.hpp
@@ -75,7 +75,7 @@ class BytesArray {
   void set(uint64_t value_id, ValueArg value);
 
   // Sweep empty pages whose modified time < (now - lifetime).
-  bool sweep(Duration lifetime);
+  void sweep(Duration lifetime);
 
  private:
   Storage *storage_;
diff --git a/lib/grnxx/map/bytes_pool.cpp b/lib/grnxx/map/bytes_pool.cpp
index 151f9e9..d00b89c 100644
--- a/lib/grnxx/map/bytes_pool.cpp
+++ b/lib/grnxx/map/bytes_pool.cpp
@@ -203,10 +203,10 @@ uint64_t BytesPool::add(ValueArg value) {
   return get_value_id(offset, size);
 }
 
-bool BytesPool::sweep(Duration lifetime) {
+void BytesPool::sweep(Duration lifetime) {
   if (header_->latest_empty_page_id == INVALID_PAGE_ID) {
     // Nothing to do.
-    return true;
+    return;
   }
   BytesPoolPageHeader * const latest_empty_page_header =
       &page_headers_->get_value(header_->latest_empty_page_id);
@@ -223,7 +223,7 @@ bool BytesPool::sweep(Duration lifetime) {
     }
     if (oldest_empty_page_header->modified_time > threshold) {
       // The remaining empty pages are not ready.
-      return true;
+      break;
     }
     const uint32_t next_oldest_empty_page_id =
         oldest_empty_page_header->next_page_id;
@@ -234,7 +234,6 @@ bool BytesPool::sweep(Duration lifetime) {
       header_->latest_empty_page_id = INVALID_PAGE_ID;
     }
   } while (header_->latest_empty_page_id != INVALID_PAGE_ID);
-  return true;
 }
 
 BytesPool::~BytesPool() {}
diff --git a/lib/grnxx/map/bytes_pool.hpp b/lib/grnxx/map/bytes_pool.hpp
index 8574175..4ede058 100644
--- a/lib/grnxx/map/bytes_pool.hpp
+++ b/lib/grnxx/map/bytes_pool.hpp
@@ -129,7 +129,7 @@ class BytesPool {
   }
 
   // Sweep empty pages whose modified time <= (now - lifetime).
-  bool sweep(Duration lifetime);
+  void sweep(Duration lifetime);
 
  private:
   Storage *storage_;
diff --git a/test/test_map.cpp b/test/test_map.cpp
index af0e8bd..6493f91 100644
--- a/test/test_map.cpp
+++ b/test/test_map.cpp
@@ -247,7 +247,7 @@ void test_bytes_pool_sweep() {
     std::uint64_t key_id = pool->add(keys[i]);
     pool->unset(key_id);
   }
-  assert(pool->sweep(grnxx::Duration(0)));
+  pool->sweep(grnxx::Duration(0));
   for (std::uint64_t i = 0; i < BYTES_POOL_NUM_KEYS; ++i) {
     std::uint64_t key_id = pool->add(keys[i]);
     key_ids.push_back(key_id);
@@ -255,7 +255,7 @@ void test_bytes_pool_sweep() {
   for (std::uint64_t i = 0; i < BYTES_POOL_NUM_KEYS; ++i) {
     pool->unset(key_ids[i]);
   }
-  assert(pool->sweep(grnxx::Duration(0)));
+  pool->sweep(grnxx::Duration(0));
 }
 
 void test_bytes_array_create() {