diff --git a/pymbolic/primitives.py b/pymbolic/primitives.py
index 5513a0492b93fafa8886a38c050df070a43b6767..f02bc98d42542fee1aaba8cafd892f7365205ff8 100644
--- a/pymbolic/primitives.py
+++ b/pymbolic/primitives.py
@@ -1103,7 +1103,7 @@ def quotient(numerator, denominator):
 
 global VALID_CONSTANT_CLASSES
 global VALID_OPERANDS
-VALID_CONSTANT_CLASSES = (int, float, complex)
+VALID_CONSTANT_CLASSES = (int, long, float, complex)
 VALID_OPERANDS = (Expression,)
 
 try: