diff --git a/include/sta/ArrayTable.hh b/include/sta/ArrayTable.hh
index 13aac268..e5746418 100644
--- a/include/sta/ArrayTable.hh
+++ b/include/sta/ArrayTable.hh
@@ -13,6 +13,7 @@
 
 #include "Vector.hh"
 #include "ObjectId.hh"
+#include "Error.hh"
 
 namespace sta {
 
@@ -42,8 +43,9 @@ public:
   size_t size() const { return size_; }
   void clear();
 
-  static constexpr ObjectId idx_bits = 10;
-  static constexpr ObjectId block_size = (1 << idx_bits);
+  static constexpr int idx_bits = 7;
+  static constexpr int block_size = (1 << idx_bits);
+  static constexpr int block_id_max = 1 << (object_id_bits - idx_bits);
 
 private:
   ArrayBlock<TYPE> *makeBlock(uint32_t size);
@@ -129,6 +131,8 @@ void
 ArrayTable<TYPE>::pushBlock(ArrayBlock<TYPE> *block)
 {
   blocks_[blocks_size_++] = block;
+  if (blocks_size_ >= block_id_max)
+    internalError("max array table block count exceeded.");
   if (blocks_size_ == blocks_capacity_) {
     size_t new_capacity = blocks_capacity_ * 1.5;
     ArrayBlock<TYPE>** new_blocks = new ArrayBlock<TYPE>*[new_capacity];
diff --git a/include/sta/ObjectId.hh b/include/sta/ObjectId.hh
index 175d1e21..f3acd5f0 100644
--- a/include/sta/ObjectId.hh
+++ b/include/sta/ObjectId.hh
@@ -19,6 +19,7 @@ typedef uint32_t BlockIdx;
 // Object index within a block.
 typedef uint32_t ObjectIdx;
 
+static constexpr int object_id_bits = sizeof(ObjectId) * 8;
 static constexpr BlockIdx block_idx_null = 0;
 static constexpr ObjectId object_id_null = 0;
 static constexpr ObjectIdx object_idx_null = 0;
diff --git a/include/sta/ObjectTable.hh b/include/sta/ObjectTable.hh
index 7b2ba4f3..764c6d38 100644
--- a/include/sta/ObjectTable.hh
+++ b/include/sta/ObjectTable.hh
@@ -43,8 +43,9 @@ public:
   void clear();
 
   // Objects are allocated in blocks of 128.
-  static constexpr ObjectId idx_bits = 7;
-  static constexpr ObjectId block_object_count = (1 << idx_bits);
+  static constexpr int idx_bits = 7;
+  static constexpr int block_object_count = (1 << idx_bits);
+  static constexpr int block_id_max = 1 << (object_id_bits - idx_bits);
 
 private:
   void makeBlock();
@@ -104,6 +105,8 @@ ObjectTable<TYPE>::makeBlock()
   BlockIdx block_index = blocks_.size();
   TableBlock<TYPE> *block = new TableBlock<TYPE>(block_index, this);
   blocks_.push_back(block);
+  if (blocks_.size() >= block_id_max)
+    internalError("max object table block count exceeded.");
   // ObjectId zero is reserved for object_id_null.
   int last = (block_index > 0) ? 0 : 1;
   for (int i = block_object_count - 1; i >= last; i--) {