diff --git a/GeneratorInterface/Core/interface/LHEWeightHelper.h b/GeneratorInterface/Core/interface/LHEWeightHelper.h
index ef3371c4095d6..f29aaf5f2f7df 100644
--- a/GeneratorInterface/Core/interface/LHEWeightHelper.h
+++ b/GeneratorInterface/Core/interface/LHEWeightHelper.h
@@ -24,9 +24,10 @@ namespace gen {
     void parseWeights();
     bool isConsistent();
     void swapHeaders();
-
+    void setFailIfInvalidXML(bool value) { failIfInvalidXML_ = value; }
   private:
     std::vector<std::string> headerLines_;
+    bool failIfInvalidXML_ = false;
   };
 }  // namespace gen
 
diff --git a/GeneratorInterface/Core/plugins/LHEWeightProductProducer.cc b/GeneratorInterface/Core/plugins/LHEWeightProductProducer.cc
index 6b25ac35c4ae0..f06d68d5e81f4 100644
--- a/GeneratorInterface/Core/plugins/LHEWeightProductProducer.cc
+++ b/GeneratorInterface/Core/plugins/LHEWeightProductProducer.cc
@@ -57,6 +57,7 @@ LHEWeightProductProducer::LHEWeightProductProducer(const edm::ParameterSet& iCon
             [this](const std::string& tag) { return mayConsume<GenWeightInfoProduct, edm::InLumi>(tag); })) {
   produces<GenWeightProduct>();
   produces<GenWeightInfoProduct, edm::Transition::BeginLuminosityBlock>();
+  weightHelper_.setFailIfInvalidXML(iConfig.getUntrackedParameter<bool>("failIfInvalidXML", false));
 }
 
 LHEWeightProductProducer::~LHEWeightProductProducer() {}
diff --git a/GeneratorInterface/Core/src/LHEWeightHelper.cc b/GeneratorInterface/Core/src/LHEWeightHelper.cc
index 5f51c6658e75c..00cd7b2ad6e6b 100644
--- a/GeneratorInterface/Core/src/LHEWeightHelper.cc
+++ b/GeneratorInterface/Core/src/LHEWeightHelper.cc
@@ -2,6 +2,7 @@
 #include <boost/algorithm/string/join.hpp>
 #include <boost/algorithm/string/replace.hpp>
 #include <iostream>
+#include <stdexcept>
 
 using namespace tinyxml2;
 
@@ -11,7 +12,11 @@ namespace gen {
   void LHEWeightHelper::parseWeights() {
     parsedWeights_.clear();
 
-    if (!isConsistent()) {
+    if (!isConsistent() && failIfInvalidXML_) {
+      throw std::runtime_error( "XML in LHE is not consistent: Most likely, tags were swapped.\n" \
+                                "To turn on fault fixing, use 'setFailIfInvalidXML(false)'\n" \
+                                "WARNING: the tag swapping may lead to weights associated with the incorrect group");
+    } else if (!isConsistent()) {
       swapHeaders();
     }
 
@@ -29,7 +34,10 @@ namespace gen {
     if (xmlError != 0) {
       std::cerr << "Error in lhe xml file" << std::endl;
       xmlDoc.PrintError();
-      return;
+      if(failIfInvalidXML_)
+        throw std::runtime_error("XML is unreadable because of above error.");
+      else
+        return;
     }
 
     std::vector<std::string> nameAlts_ = {"name", "type"};
diff --git a/GeneratorInterface/Core/test/testGenWeightProducer_cfg.py b/GeneratorInterface/Core/test/testGenWeightProducer_cfg.py
index 0c0925dc2e46e..cde648a77d08c 100644
--- a/GeneratorInterface/Core/test/testGenWeightProducer_cfg.py
+++ b/GeneratorInterface/Core/test/testGenWeightProducer_cfg.py
@@ -26,8 +26,9 @@
                 'keep GenWeightInfoProduct_test*Weights*_*_*',])
 )
 
-#process.testLHEWeights = cms.EDProducer("LHEWeightProductProducer",
-#    lheSourceLabel = cms.string("externalLHEProducer"))
+# process.testLHEWeights = cms.EDProducer("LHEWeightProductProducer",
+#    lheSourceLabel = cms.string("externalLHEProducer"),
+#    failIfValidXML = cms.untracked.bool(True))
 
 process.testGenWeights = cms.EDProducer("GenWeightProductProducer",
     genInfo = cms.InputTag("generator"),
diff --git a/PhysicsTools/NanoAOD/python/nanogen_cff.py b/PhysicsTools/NanoAOD/python/nanogen_cff.py
index ffd7a82c2b324..6e81ab1ce2023 100644
--- a/PhysicsTools/NanoAOD/python/nanogen_cff.py
+++ b/PhysicsTools/NanoAOD/python/nanogen_cff.py
@@ -11,7 +11,8 @@
     genLumiInfoHeader = cms.InputTag("generator"))
 
 lheWeights = cms.EDProducer("LHEWeightProductProducer",
-    lheSourceLabels = cms.vstring(["externalLHEProducer", "source"])
+    lheSourceLabels = cms.vstring(["externalLHEProducer", "source"]),
+    failIfInvalidXML = cms.untracked.bool(True)
     #lheWeightSourceLabels = cms.vstring(["externalLHEProducer", "source"])
 )