diff --git a/fairseq/data/dictionary.py b/fairseq/data/dictionary.py
index 7ad590a19b..3b8b741c4d 100644
--- a/fairseq/data/dictionary.py
+++ b/fairseq/data/dictionary.py
@@ -126,7 +126,7 @@ def unk_string(self, escape=False):
 
     def add_symbol(self, word, n=1, overwrite=False):
         """Adds a word to the dictionary"""
-        if word in self.indices and not overwrite:
+        if word in self.indices and overwrite:
             idx = self.indices[word]
             self.count[idx] = self.count[idx] + n
             return idx