diff --git a/setup.py b/setup.py
index 153888aae..c7f9470f7 100644
--- a/setup.py
+++ b/setup.py
@@ -152,7 +152,9 @@ GeneralizedIndex = NewType('GeneralizedIndex', int)
 SSZObject = TypeVar('SSZObject', bound=View)
 '''
 SUNDRY_CONSTANTS_FUNCTIONS = '''
-def ceillog2(x: uint64) -> uint64:
+def ceillog2(x: int) -> uint64:
+    if x < 1:
+        raise ValueError(f"ceillog2 accepts only positive values, x={x}")
     return uint64((x - 1).bit_length())
 '''
 PHASE0_SUNDRY_FUNCTIONS = '''