diff --git a/include/zasm/core/objectpool.hpp b/include/zasm/core/objectpool.hpp
index cc2e33a..bacada6 100644
--- a/include/zasm/core/objectpool.hpp
+++ b/include/zasm/core/objectpool.hpp
@@ -71,8 +71,12 @@ namespace zasm
 
         void reset()
         {
-            _blocks.clear();
-            _blocks.push_back(std::make_unique<Block>());
+            // Shrink to single block.
+            _blocks.resize(1);
+
+            // Reset slot to zero.
+            _blocks[0]->slot = 0;
+
             _freeItem = nullptr;
         }
 
diff --git a/src/zasm/src/program/program.cpp b/src/zasm/src/program/program.cpp
index 67db6e5..319d312 100644
--- a/src/zasm/src/program/program.cpp
+++ b/src/zasm/src/program/program.cpp
@@ -331,8 +331,12 @@ namespace zasm
 
         notifyObservers<true>(&Observer::onNodeDestroy, state.observer, node);
 
-        // Ensure node is not in the list anymore.
-        detach_<false>(node, state);
+        // If this is called from clear or from destructor we can skip unlinking.
+        if (!quickDestroy)
+        {
+            // Ensure node is not in the list anymore.
+            detach_<false>(node, state);
+        }
 
         // Release.
         auto* nodeToDestroy = detail::toInternal(node);
@@ -377,6 +381,11 @@ namespace zasm
             node = next;
         }
 
+        _state->head = nullptr;
+        _state->tail = nullptr;
+        _state->nextNodeId = {};
+        _state->nodeCount = 0;
+
         _state->nodeMap.clear();
         _state->sections.clear();
         _state->labels.clear();