diff --git a/deap/base.py b/deap/base.py
index ce36c8ef9..0d2a30e05 100644
--- a/deap/base.py
+++ b/deap/base.py
@@ -185,7 +185,7 @@ def getValues(self):
         return tuple(map(truediv, self.wvalues, self.weights))
 
     def setValues(self, values):
-        assert len(values) == len(self.weights)
+        assert len(values) == len(self.weights), "Assigned values have not the same length than fitness weights"
         try:
             self.wvalues = tuple(map(mul, values, self.weights))
         except TypeError: