diff --git a/libcorpus2/util/symboldictionary.h b/libcorpus2/util/symboldictionary.h
index 322e33bb5f329d789cb08d42e4797c5b08308be4..f0027a95a472213f7b5da65365c7d71ac0e974bd 100644
--- a/libcorpus2/util/symboldictionary.h
+++ b/libcorpus2/util/symboldictionary.h
@@ -158,7 +158,7 @@ template <typename IndexT>
 const std::string& SymbolDictionary<IndexT>::get_string(IndexT id) const
 {
 	size_t idx = static_cast<size_t>(id);
-	if (id < data_.size()) {
+	if (idx < data_.size()) {
 		return data_[idx];
 	} else {
 		return nullstr;