diff --git a/README.md b/README.md
index 15a307a18..0422669f4 100644
--- a/README.md
+++ b/README.md
@@ -90,7 +90,7 @@ Procedures for each standard are provided by the following R7RS-style libraries:
 cmake -B build -DCMAKE_BUILD_TYPE=Release
 cd build
 make package
-sudo apt install build/meevax_0.5.257_amd64.deb
+sudo apt install build/meevax_0.5.258_amd64.deb
 ```
 
 or
@@ -122,9 +122,9 @@ sudo rm -rf /usr/local/share/meevax
 
 | Target Name | Description
 |-------------|-------------
-| `all`       | Build shared-library `libmeevax.0.5.257.so` and executable `meevax`
+| `all`       | Build shared-library `libmeevax.0.5.258.so` and executable `meevax`
 | `test`      | Test executable `meevax`
-| `package`   | Generate debian package `meevax_0.5.257_amd64.deb`
+| `package`   | Generate debian package `meevax_0.5.258_amd64.deb`
 | `install`   | Copy files into `/usr/local` directly
 
 ## Usage
diff --git a/VERSION b/VERSION
index 5138cc438..2b772e508 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.5.257
+0.5.258
diff --git a/include/meevax/memory/collector.hpp b/include/meevax/memory/collector.hpp
index 45c8df39f..45358e23a 100644
--- a/include/meevax/memory/collector.hpp
+++ b/include/meevax/memory/collector.hpp
@@ -409,7 +409,7 @@ inline namespace memory
        0x0000'0000'0000'0000 ~ 0x7FFF'FFFF'FFFF'FFFF
     */
     template <typename T>
-    using pointer_set = integer_set<T const*, 15, 16, 16>;
+    using pointer_set = integer_set<T const*, log2(0x7FFF), log2(0xFFFF), log2(0xFFFF)>;
 
   private:
     static inline pointer_set<top> objects {};
diff --git a/include/meevax/memory/integer_set.hpp b/include/meevax/memory/integer_set.hpp
index 3199dbd4f..592779b0f 100644
--- a/include/meevax/memory/integer_set.hpp
+++ b/include/meevax/memory/integer_set.hpp
@@ -75,23 +75,14 @@ inline namespace memory
 
       constexpr const_iterator() = default;
 
-      explicit const_iterator(integer_set const* container, std::size_t i) noexcept
-        : data { container->data }
-        , max  { container->max }
-        , i    { i }
-      {
-        assert(i <= N);
-        increment_unless_truthy();
-      }
-
       template <typename... Ts>
-      explicit const_iterator(integer_set const* container, std::size_t i, std::size_t j, Ts&&... xs) noexcept
+      explicit const_iterator(integer_set const* container, std::size_t i, Ts&&... xs) noexcept
         : data { container->data }
         , max  { container->max }
         , i    { i }
       {
         assert(i <= N);
-        increment_unless_truthy(j, std::forward<decltype(xs)>(xs)...);
+        increment_unless_truthy(std::forward<decltype(xs)>(xs)...);
       }
 
       explicit const_iterator(integer_set const* container) noexcept
@@ -103,35 +94,35 @@ inline namespace memory
         assert(iter.data);
       }
 
-      auto increment_unless_truthy() noexcept -> void
+      template <typename... Ts>
+      auto increment_unless_truthy(Ts&&... xs) noexcept -> void
       {
         assert(data);
 
-        if (good())
+        if constexpr (0 < sizeof...(Ts))
         {
-          for (; i <= max; ++i)
+          if (not good() or not data[i] or not (iter = data[i]->lower_bound(std::forward<decltype(xs)>(xs)...)).good())
           {
-            if (data[i] and (iter = data[i]->lower_bound(0)).good())
-            {
-              return;
-            }
+            ++i;
+            increment_unless_truthy();
           }
-
-          i = N;
         }
+        else
+        {
+          if (good())
+          {
+            for (; i <= max; ++i)
+            {
+              if (data[i] and (iter = data[i]->lower_bound(0)).good())
+              {
+                return;
+              }
+            }
 
-        iter = {};
-      }
-
-      template <typename... Ts>
-      auto increment_unless_truthy(std::size_t j, Ts&&... xs) noexcept -> void
-      {
-        assert(data);
+            i = N;
+          }
 
-        if (not good() or not data[i] or not (iter = data[i]->lower_bound(j, std::forward<decltype(xs)>(xs)...)).good())
-        {
-          ++i;
-          increment_unless_truthy();
+          iter = {};
         }
       }