diff --git a/spacy/strings.pyx b/spacy/strings.pyx
index e5792aa9a..e15f88837 100644
--- a/spacy/strings.pyx
+++ b/spacy/strings.pyx
@@ -49,6 +49,7 @@ cdef class SymbolMap:
 
 
 cdef class StringStore:
+    '''Map strings to and from integer IDs.'''
     def __init__(self):
         self.mem = Pool()
         self._map = PreshMap()