diff --git a/include/cantera/zeroD/ReactorNet.h b/include/cantera/zeroD/ReactorNet.h
index df244586b..0a936f17f 100644
--- a/include/cantera/zeroD/ReactorNet.h
+++ b/include/cantera/zeroD/ReactorNet.h
@@ -168,6 +168,10 @@ public:
         if (!m_init) {
             initialize();
         }
+        if (p >= m_sensIndex.size()) {
+            throw IndexError("ReactorNet::sensitivity",
+                             "m_sensIndex", p, m_sensIndex.size()-1);
+        }
         return m_integ->sensitivity(k, m_sensIndex[p])/m_integ->solution(k);
     }