diff --git a/src/extractor/extraction_containers.cpp b/src/extractor/extraction_containers.cpp
index 8b8c6b068..138552ae7 100644
--- a/src/extractor/extraction_containers.cpp
+++ b/src/extractor/extraction_containers.cpp
@@ -47,7 +47,9 @@ ExtractionContainers::ExtractionContainers()
 {
     // Check if stxxl can be instantiated
     stxxl::vector<unsigned> dummy_vector;
-    // Insert the empty string, it has no data and is zero length
+    // Insert three empty strings for name, destination and pronunciation
+    name_lengths.push_back(0);
+    name_lengths.push_back(0);
     name_lengths.push_back(0);
 }
 
diff --git a/src/extractor/extractor_callbacks.cpp b/src/extractor/extractor_callbacks.cpp
index a22d25924..375614ae9 100644
--- a/src/extractor/extractor_callbacks.cpp
+++ b/src/extractor/extractor_callbacks.cpp
@@ -27,6 +27,7 @@ namespace extractor
 ExtractorCallbacks::ExtractorCallbacks(ExtractionContainers &extraction_containers)
     : external_memory(extraction_containers)
 {
+    // we reserved 0, 1, 2 for the empty case
     string_map[MapKey("", "")] = 0;
 }