diff --git a/doc/OpenSTA.odt b/doc/OpenSTA.odt
index 5c899c42..df2413a4 100644
Binary files a/doc/OpenSTA.odt and b/doc/OpenSTA.odt differ
diff --git a/doc/OpenSTA.pdf b/doc/OpenSTA.pdf
index 598b21c5..cd69a845 100644
Binary files a/doc/OpenSTA.pdf and b/doc/OpenSTA.pdf differ
diff --git a/include/sta/Sdc.hh b/include/sta/Sdc.hh
index b2de4c8d..b00e3bad 100644
--- a/include/sta/Sdc.hh
+++ b/include/sta/Sdc.hh
@@ -224,6 +224,9 @@ public:
 			const RiseFall *rf,
 			const EarlyLate *early_late) const;
   void unsetTimingDerate();
+  static void moveDeratingFactors(Sdc *from,
+                                  Sdc *to);
+
   void setInputSlew(Port *port, const RiseFallBoth *rf,
 		    const MinMaxAll *min_max, float slew);
   // Set the rise/fall drive resistance on design port.
diff --git a/sdc/Sdc.cc b/sdc/Sdc.cc
index b69db1c7..f31f29f0 100644
--- a/sdc/Sdc.cc
+++ b/sdc/Sdc.cc
@@ -686,6 +686,28 @@ Sdc::unsetTimingDerate()
   deleteDeratingFactors();
 }
 
+void
+Sdc::moveDeratingFactors(Sdc *from,
+                         Sdc *to)
+{
+  if (from->derating_factors_) {
+    to->derating_factors_ = from->derating_factors_;
+    from->derating_factors_ = nullptr;
+  }
+  if (from->net_derating_factors_) {
+    to->net_derating_factors_ = from->net_derating_factors_;
+    from->net_derating_factors_ = nullptr;
+  }
+  if (from->inst_derating_factors_) {
+    to->inst_derating_factors_ = from->inst_derating_factors_;
+    from->inst_derating_factors_ = nullptr;
+  }
+  if (from->cell_derating_factors_) {
+    to->cell_derating_factors_ = from->cell_derating_factors_;
+    from->cell_derating_factors_ = nullptr;
+  }
+}
+
 void
 Sdc::deleteDeratingFactors()
 {
diff --git a/search/MakeTimingModel.cc b/search/MakeTimingModel.cc
index 1d196e20..0b37ebe2 100644
--- a/search/MakeTimingModel.cc
+++ b/search/MakeTimingModel.cc
@@ -93,6 +93,7 @@ MakeTimingModel::saveSdc()
   sdc_backup_ = new Sdc(this);
   Sdc::movePortDelays(sdc_, sdc_backup_);
   Sdc::movePortExtCaps(sdc_, sdc_backup_);
+  Sdc::moveDeratingFactors(sdc_, sdc_backup_);
   sta_->delaysInvalid();
 }
 
@@ -101,6 +102,7 @@ MakeTimingModel::restoreSdc()
 {
   Sdc::movePortDelays(sdc_backup_, sdc_);
   Sdc::movePortExtCaps(sdc_backup_, sdc_);
+  Sdc::moveDeratingFactors(sdc_backup_, sdc_);
   sta_->delaysInvalid();
   delete sdc_backup_;
 }