diff --git a/src/handles.h b/src/handles.h
index aca869026e..6f3044cb8a 100644
--- a/src/handles.h
+++ b/src/handles.h
@@ -246,7 +246,7 @@ Handle<FixedArray> AddKeysFromJSArray(Handle<FixedArray>,
 // if none exists.
 Handle<JSValue> GetScriptWrapper(Handle<Script> script);
 
-// Script line number computations.
+// Script line number computations. Note that the line number is zero-based.
 void InitScriptLineEnds(Handle<Script> script);
 // For string calculates an array of line end positions. If the string
 // does not end with a new line character, this character may optionally be
diff --git a/src/isolate.cc b/src/isolate.cc
index 30c60b691e..766c072828 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -1136,12 +1136,12 @@ void Isolate::DoThrow(Object* exception, MessageLocation* location) {
             "Extension or internal compilation error: %s in %s at line %d.\n",
             *String::cast(exception)->ToCString(),
             *String::cast(location->script()->name())->ToCString(),
-            line_number);
+            line_number + 1);
       } else {
         OS::PrintError(
             "Extension or internal compilation error in %s at line %d.\n",
             *String::cast(location->script()->name())->ToCString(),
-            line_number);
+            line_number + 1);
       }
     }
   }