diff --git a/src/collocatordb.h b/src/collocatordb.h
index 8bb3402..74f2f0e 100644
--- a/src/collocatordb.h
+++ b/src/collocatordb.h
@@ -131,5 +131,6 @@
 extern char *get_version();
 extern uint64_t get_word_id(COLLOCATORDB *db, const char *word);
 extern uint64_t get_corpus_size(COLLOCATORDB *db);
+extern uint64_t get_word_frequency(COLLOCATORDB *db, uint64_t w1);
 
 #endif