diff --git a/src/constitutive/TACSBladeStiffenedShellConstitutive.h b/src/constitutive/TACSBladeStiffenedShellConstitutive.h
index 43f00702..b9503e14 100644
--- a/src/constitutive/TACSBladeStiffenedShellConstitutive.h
+++ b/src/constitutive/TACSBladeStiffenedShellConstitutive.h
@@ -1397,8 +1397,8 @@ class TACSBladeStiffenedShellConstitutive : public TACSShellConstitutive {
   std::function<TacsScalar(const TacsScalar[],TacsScalar[])> evalLocalPanelBucklingStrainSens;
   std::function<TacsScalar(const TacsScalar[],TacsScalar[])> evalGlobalPanelBucklingStrainSens;
   std::function<TacsScalar(const TacsScalar[],TacsScalar[])> evalStiffenerCripplingStrainSens;
-  std::function<void(int,TacsScalar,const double[],const TacsScalar[],const TacsScalar[],int dvLen,TacsScalar[])> addLocalPanelBucklingDVSens;
-  std::function<void(int,TacsScalar,const double[],const TacsScalar[],const TacsScalar[],int dvLen,TacsScalar[])> addGlobalPanelBucklingDVSens;
+  std::function<void(int,TacsScalar,const double[],const TacsScalar[],const TacsScalar[],int,TacsScalar[])> addLocalPanelBucklingDVSens;
+  std::function<void(int,TacsScalar,const double[],const TacsScalar[],const TacsScalar[],int,TacsScalar[])> addGlobalPanelBucklingDVSens;
   std::function<void(const TacsScalar, const TacsScalar[], TacsScalar[])> addStiffenerCripplingDVSens;
 
   static const char* const constName;  ///< Constitutive model name
diff --git a/src/constitutive/TACSGPBladeStiffenedShellConstitutive.cpp b/src/constitutive/TACSGPBladeStiffenedShellConstitutive.cpp
index e2653df3..5ea989e3 100644
--- a/src/constitutive/TACSGPBladeStiffenedShellConstitutive.cpp
+++ b/src/constitutive/TACSGPBladeStiffenedShellConstitutive.cpp
@@ -210,10 +210,7 @@ TacsScalar TACSGPBladeStiffenedShellConstitutive::_evalGlobalPanelBuckling(const
   TacsScalar N12CritGlobal = computeCriticalGlobalShearLoad(
     D11Global, D22p, b, rho0Global,
     xiGlobal, gamma, zetaPanel
-  ); 
-
-  printf("N1CritGLobal = %.8e\n", N1CritGlobal);
-  printf("N12CritGlobal = %.8e\n", N12CritGlobal);
+  );
 
   // compute the combined loading buckling failure index
   return this->bucklingEnvelope(-panelStress[0], N1CritGlobal,
@@ -1439,7 +1436,7 @@ TACSGPBladeStiffenedShellConstitutive::computeStiffenerStiffnessRatioSens(
   // backpropagate to intermediate quantities As, Is, zs, zn
   TacsScalar AsSens = IstotSens * (zn - zs) * (zn - zs);
   TacsScalar IsSens = IstotSens;
-  TacsScalar zsSens = IstotSens * As * 2.0 * (zs - zn);
+  TacsScalar zsSens = -1.0 * IstotSens * As * 2.0 * (zs - zn);
   *znSens += IstotSens * As * 2.0 * (zn - zs);
 
   // backpropgate from intermediate quantities to DVs or material, etc.
diff --git a/tacs/constitutive.pyx b/tacs/constitutive.pyx
index 50247e79..f1f54893 100644
--- a/tacs/constitutive.pyx
+++ b/tacs/constitutive.pyx
@@ -1433,6 +1433,7 @@ cdef class GPBladeStiffenedShellConstitutive(ShellConstitutive):
         int stiffenerThickNum = -1,
         np.ndarray[int, ndim=1, mode='c'] stiffenerPlyFracNums = None,
         int panelWidthNum = -1,
+        bool CPTstiffenerCrippling = False,
         PanelGPs panelGPs = None,
         ):
 
@@ -1489,6 +1490,7 @@ cdef class GPBladeStiffenedShellConstitutive(ShellConstitutive):
             panelWidth,
             panelWidthNum,
             flangeFraction,
+            CPTstiffenerCrippling,
             panel_gp_ptr,
         )
         # copy pointers to all superclasses
diff --git a/tacs/cpp_headers/constitutive.pxd b/tacs/cpp_headers/constitutive.pxd
index f879ed76..4f6caf9f 100644
--- a/tacs/cpp_headers/constitutive.pxd
+++ b/tacs/cpp_headers/constitutive.pxd
@@ -252,6 +252,7 @@ cdef extern from "TACSGPBladeStiffenedShellConstitutive.h":
             TacsScalar, # panelWidth
             int, # panelWidthNum
             TacsScalar, # flangeFraction,
+            bool, # CPTstiffenerCrippling
             TACSPanelGPs*, # panelGPs object container
         )
         TacsScalar nondimCriticalGlobalAxialLoad(TacsScalar rho_0, TacsScalar xi, TacsScalar gamma, TacsScalar zeta)
diff --git a/tests/constitutive_tests/test_gp_blade_shell_constitutive.py b/tests/constitutive_tests/test_gp_blade_shell_constitutive.py
index 5f6f24d6..a32b39b8 100644
--- a/tests/constitutive_tests/test_gp_blade_shell_constitutive.py
+++ b/tests/constitutive_tests/test_gp_blade_shell_constitutive.py
@@ -205,7 +205,7 @@ def get_con(self, ply):
             self.stiffenerThicknessNum,
             self.stiffenerPlyFracNums,
             self.panelWidthNum,
-            self.panelGPs,
+            panelGPs=self.panelGPs,
         )
         # Set the KS weight really low so that all failure modes make a
         # significant contribution to the failure function derivatives