diff --git a/scripts/mbedtls_dev/bignum_common.py b/scripts/mbedtls_dev/bignum_common.py
index 5319ec6..aa2cd25 100644
--- a/scripts/mbedtls_dev/bignum_common.py
+++ b/scripts/mbedtls_dev/bignum_common.py
@@ -68,7 +68,8 @@
 
 def limbs_mpi(val: int, bits_in_limb: int) -> int:
     """Return the number of limbs required to store value."""
-    return (val.bit_length() + bits_in_limb - 1) // bits_in_limb
+    bit_length = max(val.bit_length(), 1)
+    return (bit_length + bits_in_limb - 1) // bits_in_limb
 
 def combination_pairs(values: List[T]) -> List[Tuple[T, T]]:
     """Return all pair combinations from input values."""