diff --git a/moses/src/LM/Implementation.cpp b/moses/src/LM/Implementation.cpp
index f649eef06..589ed375a 100644
--- a/moses/src/LM/Implementation.cpp
+++ b/moses/src/LM/Implementation.cpp
@@ -100,7 +100,7 @@ void LanguageModelImplementation::CalcScore(const Phrase &phrase, float &fullSco
       if (word == GetSentenceStartArray()) {
         // do nothing, don't include prob for <s> unigram
         if (currPos != 0) {
-          std::cerr << "Your data contains <s> in a position other than the first word." << std::endl;
+          std::cerr << "Either your data contains <s> in a position other than the first word or your language model is missing <s>.  Did you build your ARPA using IRSTLM and forget to run add-start-end.sh?" << std::endl;
           abort();
         }
       } else {
diff --git a/moses/src/LM/Ken.cpp b/moses/src/LM/Ken.cpp
index b8a78af19..9aa4d2788 100644
--- a/moses/src/LM/Ken.cpp
+++ b/moses/src/LM/Ken.cpp
@@ -198,7 +198,7 @@ template <class Model> void LanguageModelKen<Model>::CalcScore(const Phrase &phr
     } else {
       lm::WordIndex index = TranslateID(word);
       if (index == m_ngram->GetVocabulary().BeginSentence()) {
-        std::cerr << "Your data contains <s> in a position other than the first word." << std::endl;
+        std::cerr << "Either your data contains <s> in a position other than the first word or your language model is missing <s>.  Did you build your ARPA using IRSTLM and forget to run add-start-end.sh?" << std::endl;
         abort();
       }
       float score = TransformLMScore(m_ngram->Score(*state0, index, *state1));