diff --git a/GeneratorInterface/Pythia8Interface/src/Py8HMC3InterfaceBase.cc b/GeneratorInterface/Pythia8Interface/src/Py8HMC3InterfaceBase.cc
index 12eceee7cc925..28994f790186d 100644
--- a/GeneratorInterface/Pythia8Interface/src/Py8HMC3InterfaceBase.cc
+++ b/GeneratorInterface/Pythia8Interface/src/Py8HMC3InterfaceBase.cc
@@ -27,7 +27,11 @@ namespace gen {
 
     if (ps.exists("useEvtGenPlugin")) {
       useEvtGen = true;
-      string evtgenpath(std::getenv("EVTGENDATA"));
+      auto env = std::getenv("EVTGENDATA");
+      if (not env) {
+        throw cms::Exception("EvtGenMissingEnv") << "The environment variable EVTGENDATA must be defined";
+      }
+      string evtgenpath(env);
       evtgenDecFile = evtgenpath + string("/DECAY_2010.DEC");
       evtgenPdlFile = evtgenpath + string("/evt.pdl");
 
diff --git a/GeneratorInterface/Pythia8Interface/src/Py8InterfaceBase.cc b/GeneratorInterface/Pythia8Interface/src/Py8InterfaceBase.cc
index 6b5cbb999925a..70e83da02a06c 100644
--- a/GeneratorInterface/Pythia8Interface/src/Py8InterfaceBase.cc
+++ b/GeneratorInterface/Pythia8Interface/src/Py8InterfaceBase.cc
@@ -31,7 +31,11 @@ namespace gen {
 
     if (ps.exists("useEvtGenPlugin")) {
       useEvtGen = true;
-      string evtgenpath(std::getenv("EVTGENDATA"));
+      auto env = std::getenv("EVTGENDATA");
+      if (not env) {
+        throw cms::Exception("EvtGenMissingEnv") << "The environment variable EVTGENDATA must be defined";
+      }
+      string evtgenpath(env);
       evtgenDecFile = evtgenpath + string("/DECAY_2010.DEC");
       evtgenPdlFile = evtgenpath + string("/evt.pdl");