diff --git a/interface/TextMiningService.py b/interface/TextMiningService.py
index 8d90c300067b24a763f411b7a51ed6da04b19c81..2c2ac4df901ab1dd6c6a6b2ca079c48ea73a11af 100644
--- a/interface/TextMiningService.py
+++ b/interface/TextMiningService.py
@@ -27,7 +27,7 @@ class TextMiningService(metaclass=ABCMeta):
         pass
 
     @abstractmethod
-    def get_co_occurrences(self, entity: str, limit: int = 20, types: List[str] = []s) -> List[CoOccurrence]:
+    def get_co_occurrences(self, entity: str, limit: int = 20, types: List[str] = None) -> List[CoOccurrence]:
         """
         Co-occurrences at publication level.