diff --git a/include/cantera/zeroD/ReactorNet.h b/include/cantera/zeroD/ReactorNet.h
index ead3580eb..877fd2cf9 100644
--- a/include/cantera/zeroD/ReactorNet.h
+++ b/include/cantera/zeroD/ReactorNet.h
@@ -146,6 +146,9 @@ public:
     //! Return the sensitivity of the *k*-th solution component with
     //! respect to the *p*-th sensitivity parameter.
     double sensitivity(size_t k, size_t p) {
+        if (!m_init) {
+            initialize();
+        }
         return m_integ->sensitivity(k, m_sensIndex[p])/m_integ->solution(k);
     }
 
diff --git a/src/numerics/CVodesIntegrator.cpp b/src/numerics/CVodesIntegrator.cpp
index 4052d249b..6dbe25a78 100644
--- a/src/numerics/CVodesIntegrator.cpp
+++ b/src/numerics/CVodesIntegrator.cpp
@@ -508,6 +508,10 @@ int CVodesIntegrator::nEvals() const
 
 double CVodesIntegrator::sensitivity(size_t k, size_t p)
 {
+    if (m_time == m_t0) {
+        // calls to CVodeGetSens are only allowed after a successful time step.
+        return 0.0;
+    }
     if (!m_sens_ok && m_np) {
 #if SUNDIALS_VERSION <= 23
         int flag = CVodeGetSens(m_cvode_mem, m_time, m_yS);
diff --git a/src/zeroD/ReactorNet.cpp b/src/zeroD/ReactorNet.cpp
index 2887027d3..03a34e6aa 100644
--- a/src/zeroD/ReactorNet.cpp
+++ b/src/zeroD/ReactorNet.cpp
@@ -256,6 +256,9 @@ void ReactorNet::getInitialConditions(doublereal t0,
 
 size_t ReactorNet::globalComponentIndex(const string& species, size_t reactor)
 {
+    if (!m_init) {
+        initialize();
+    }
     size_t start = 0;
     size_t n;
     for (n = 0; n < reactor; n++) {