diff --git a/ibis/expr/datatypes/core.py b/ibis/expr/datatypes/core.py
index 44e7d571fd39..162bfdf5e39c 100644
--- a/ibis/expr/datatypes/core.py
+++ b/ibis/expr/datatypes/core.py
@@ -654,7 +654,7 @@ def largest(self):
     @property
     def bounds(self):
         exp = self.nbytes * 8
-        upper = 1 << exp
+        upper = (1 << exp) - 1
         return Bounds(lower=0, upper=upper)