diff --git a/sageopt/symbolic/polynomials.py b/sageopt/symbolic/polynomials.py
index e1fcc19..6891360 100644
--- a/sageopt/symbolic/polynomials.py
+++ b/sageopt/symbolic/polynomials.py
@@ -340,7 +340,7 @@ def __call__(self, x):
             temp1 = np.power(x, self.alpha)
             temp2 = np.prod(temp1, axis=1)
             temp3 = self.c * temp2
-            if temp3.dtype in __NUMERIC_TYPES__:
+            if temp3.dtype is not object:
                 val = np.sum(temp3)
                 return val
             else: