diff --git a/include/sta/Liberty.hh b/include/sta/Liberty.hh
index 5f10462c..38bcfa39 100644
--- a/include/sta/Liberty.hh
+++ b/include/sta/Liberty.hh
@@ -179,7 +179,7 @@ public:
 			float wire_delay) const;
   // Check for supported axis variables.
   // Return true if axes are supported.
-  static bool checkSlewDegradationAxes(TablePtr table);
+  static bool checkSlewDegradationAxes(const TablePtr &table);
 
   float defaultInputPinCap() const { return default_input_pin_cap_; }
   void setDefaultInputPinCap(float cap);
@@ -788,7 +788,7 @@ public:
   void setRelatedGroundPin(const char *related_ground_pin);
   const char *relatedPowerPin() const { return related_power_pin_; }
   void setRelatedPowerPin(const char *related_power_pin);
-  ReceiverModelPtr receiverModel() const { return receiver_model_; }
+  const ReceiverModel *receiverModel() const { return receiver_model_.get(); }
   void setReceiverModel(ReceiverModelPtr receiver_model);
   DriverWaveform *driverWaveform(const RiseFall *rf) const;
   void setDriverWaveform(DriverWaveform *driver_waveform,
@@ -1017,11 +1017,14 @@ public:
   ~TableTemplate();
   const char *name() const { return name_; }
   void setName(const char *name);
-  TableAxisPtr axis1() const { return axis1_; }
+  const TableAxis *axis1() const { return axis1_.get(); }
+  TableAxisPtr axis1ptr() const { return axis1_; }
   void setAxis1(TableAxisPtr axis);
-  TableAxisPtr axis2() const { return axis2_; }
+  const TableAxis *axis2() const { return axis2_.get(); }
+  TableAxisPtr axis2ptr() const { return axis2_; }
   void setAxis2(TableAxisPtr axis);
-  TableAxisPtr axis3() const { return axis3_; }
+  const TableAxis *axis3() const { return axis3_.get(); }
+  TableAxisPtr axis3ptr() const { return axis3_; }
   void setAxis3(TableAxisPtr axis);
 
 protected:
@@ -1065,9 +1068,9 @@ public:
   OcvDerate(const char *name);
   ~OcvDerate();
   const char *name() const { return name_; }
-  TablePtr derateTable(const RiseFall *rf,
-                       const EarlyLate *early_late,
-                       PathType path_type);
+  const Table *derateTable(const RiseFall *rf,
+                           const EarlyLate *early_late,
+                           PathType path_type);
   void setDerateTable(const RiseFall *rf,
 		      const EarlyLate *early_late,
 		      PathType path_type,
diff --git a/include/sta/TableModel.hh b/include/sta/TableModel.hh
index 0202dd46..b7d91e6b 100644
--- a/include/sta/TableModel.hh
+++ b/include/sta/TableModel.hh
@@ -77,11 +77,11 @@ public:
 
   const TableModel *delayModel() const { return delay_model_; }
   const TableModel *slewModel() const { return slew_model_;  }
-  ReceiverModelPtr receiverModel() const { return receiver_model_; }
+  const ReceiverModel *receiverModel() const { return receiver_model_.get(); }
   OutputWaveforms *outputWaveforms() const { return output_waveforms_; }
   // Check the axes before making the model.
   // Return true if the model axes are supported.
-  static bool checkAxes(const TablePtr table);
+  static bool checkAxes(const TablePtr &table);
 
 protected:
   void maxCapSlew(float in_slew,
@@ -317,6 +317,7 @@ public:
   Table1 &operator= (Table1 &&table);
   int order() const override { return 1; }
   const TableAxis *axis1() const override { return axis1_.get(); }
+  const TableAxisPtr axis1ptr() const { return axis1_; }
   float value(size_t axis_index1,
               size_t axis_index2,
               size_t axis_index3) const override;
@@ -486,8 +487,8 @@ public:
                   Table1 *ref_times);
   ~OutputWaveforms();
   const RiseFall *rf() const { return rf_; }
-  TableAxisPtr slewAxis() const { return slew_axis_; }
-  TableAxisPtr capAxis() const { return cap_axis_; }
+  const TableAxis *slewAxis() const { return slew_axis_.get(); }
+  const TableAxis *capAxis() const { return cap_axis_.get(); }
   Table1 voltageWaveform(float in_slew,
                          float load_cap);
   float voltageTime(float in_slew,
@@ -503,7 +504,7 @@ public:
                        float volt);
   float referenceTime(float slew);
   void setVdd(float vdd);
-  static bool checkAxes(TableTemplate *tbl_template);
+  static bool checkAxes(const TableTemplate *tbl_template);
 
 private:
   float voltageTime1(float voltage,
diff --git a/liberty/Liberty.cc b/liberty/Liberty.cc
index 8f5283b3..b9125ab5 100644
--- a/liberty/Liberty.cc
+++ b/liberty/Liberty.cc
@@ -391,7 +391,7 @@ LibertyLibrary::degradeWireSlew(const TableModel *model,
 // Check for supported axis variables.
 // Return true if axes are supported.
 bool
-LibertyLibrary::checkSlewDegradationAxes(TablePtr table)
+LibertyLibrary::checkSlewDegradationAxes(const TablePtr &table)
 {
   switch (table->order()) {
   case 0:
@@ -3064,12 +3064,12 @@ OcvDerate::~OcvDerate()
   stringDelete(name_);
 }
 
-TablePtr
+const Table *
 OcvDerate::derateTable(const RiseFall *rf,
 		       const EarlyLate *early_late,
 		       PathType path_type)
 {
-  return derate_[rf->index()][early_late->index()][int(path_type)];
+  return derate_[rf->index()][early_late->index()][int(path_type)].get();
 }
 
 void
diff --git a/liberty/LibertyReader.cc b/liberty/LibertyReader.cc
index f25cc79f..f0b026aa 100644
--- a/liberty/LibertyReader.cc
+++ b/liberty/LibertyReader.cc
@@ -4217,13 +4217,15 @@ LibertyReader::beginTable(LibertyGroup *group,
   if (library_ && template_name) {
     tbl_template_ = library_->findTableTemplate(template_name, type);
     if (tbl_template_) {
-      axis_[0] = tbl_template_->axis1();
-      axis_[1] = tbl_template_->axis2();
-      axis_[2] = tbl_template_->axis3();
+      axis_[0] = tbl_template_->axis1ptr();
+      axis_[1] = tbl_template_->axis2ptr();
+      axis_[2] = tbl_template_->axis3ptr();
     }
     else {
       libWarn(122, group, "table template %s not found.", template_name);
-      axis_[0] = axis_[1] = axis_[2] = nullptr;
+      axis_[0] = nullptr;
+      axis_[1] = nullptr;
+      axis_[2] = nullptr;
     }
     clearAxisValues();
     table_ = nullptr;
@@ -4236,6 +4238,9 @@ LibertyReader::endTable()
 {
   table_ = nullptr;
   tbl_template_ = nullptr;
+  axis_[0] = nullptr;
+  axis_[1] = nullptr;
+  axis_[2] = nullptr;
 }
 
 void
diff --git a/liberty/LibertyWriter.cc b/liberty/LibertyWriter.cc
index 48bdce86..2a05a59c 100644
--- a/liberty/LibertyWriter.cc
+++ b/liberty/LibertyWriter.cc
@@ -46,7 +46,7 @@ protected:
   void writeHeader();
   void writeFooter();
   void writeTableTemplates();
-  void writeTableTemplate(TableTemplate *tbl_template);
+  void writeTableTemplate(const TableTemplate *tbl_template);
   void writeBusDcls();
   void writeCells();
   void writeCell(const LibertyCell *cell);
@@ -60,7 +60,7 @@ protected:
   void writeTableModel0(const TableModel *model);
   void writeTableModel1(const TableModel *model);
   void writeTableModel2(const TableModel *model);
-  void writeTableAxis(TableAxisPtr axis,
+  void writeTableAxis(const TableAxis *axis,
                       int index);
 
   const char *asString(bool value);
@@ -197,11 +197,11 @@ LibertyWriter::writeTableTemplates()
 }
 
 void
-LibertyWriter::writeTableTemplate(TableTemplate *tbl_template)
+LibertyWriter::writeTableTemplate(const TableTemplate *tbl_template)
 {
-  TableAxisPtr axis1 = tbl_template->axis1();
-  TableAxisPtr axis2 = tbl_template->axis2();
-  TableAxisPtr axis3 = tbl_template->axis3();
+  const TableAxis *axis1 = tbl_template->axis1();
+  const TableAxis *axis2 = tbl_template->axis2();
+  const TableAxis *axis3 = tbl_template->axis3();
   // skip scalar templates
   if (axis1) {
     fprintf(stream_, "  lu_table_template(%s) {\n", tbl_template->name());
@@ -224,7 +224,7 @@ LibertyWriter::writeTableTemplate(TableTemplate *tbl_template)
 }
 
 void
-LibertyWriter::writeTableAxis(TableAxisPtr axis,
+LibertyWriter::writeTableAxis(const TableAxis *axis,
                               int index)
 {
   fprintf(stream_, "    index_%d (\"", index);
diff --git a/liberty/TableModel.cc b/liberty/TableModel.cc
index 42e30724..4d7fe4df 100644
--- a/liberty/TableModel.cc
+++ b/liberty/TableModel.cc
@@ -318,7 +318,7 @@ GateTableModel::axisValue(const TableAxis *axis,
 }
 
 bool
-GateTableModel::checkAxes(const TablePtr table)
+GateTableModel::checkAxes(const TablePtr &table)
 {
   const TableAxis *axis1 = table->axis1();
   const TableAxis *axis2 = table->axis2();
@@ -1606,11 +1606,11 @@ OutputWaveforms::~OutputWaveforms()
 }
 
 bool
-OutputWaveforms::checkAxes(TableTemplate *tbl_template)
+OutputWaveforms::checkAxes(const TableTemplate *tbl_template)
 {
-  TableAxisPtr axis1 = tbl_template->axis1();
-  TableAxisPtr axis2 = tbl_template->axis2();
-  TableAxisPtr axis3 = tbl_template->axis3();
+  const TableAxis *axis1 = tbl_template->axis1();
+  const TableAxis *axis2 = tbl_template->axis2();
+  const TableAxis *axis3 = tbl_template->axis3();
   return (axis1 && axis1->variable() == TableAxisVariable::input_net_transition
           && axis2->variable() == TableAxisVariable::time
           && axis3 == nullptr)