diff --git a/chainladder/core/common.py b/chainladder/core/common.py
index f32b3637..54296a2d 100644
--- a/chainladder/core/common.py
+++ b/chainladder/core/common.py
@@ -202,7 +202,7 @@ def set_backend(self, backend, inplace=False, deep=False, **kwargs):
     def _validate_assumption(self, triangle, value, axis):
         if type(value) in (int, float, str):
             arr = np.repeat(value, triangle.shape[axis])
-        if type(value) in (list, tuple, set, np.array):
+        if type(value) in (list, tuple, set, np.ndarray):
             arr = np.array(value)
         if type(value) is dict:
             arr = np.array([value[a] for a in triangle._get_axis_value(axis)])
@@ -212,4 +212,4 @@ def _validate_assumption(self, triangle, value, axis):
             arr = arr[None, None, None]
         if axis == 2:
             arr = arr[None, None, :, None]
-        return arr
\ No newline at end of file
+        return arr