diff --git a/sklearn/decomposition/_base.py b/sklearn/decomposition/_base.py
index 4f17d3df7ba80..13d4768e6438f 100644
--- a/sklearn/decomposition/_base.py
+++ b/sklearn/decomposition/_base.py
@@ -77,7 +77,7 @@ def get_precision(self):
         return precision
 
     @abstractmethod
-    def fit(X, y=None):
+    def fit(self, X, y=None):
         """Placeholder for fit. Subclasses should implement this method!
 
         Fit the model with X.