diff --git a/tips/TIP-0046/tip-0046.md b/tips/TIP-0046/tip-0046.md
index cb4a8a033..34f3d381b 100644
--- a/tips/TIP-0046/tip-0046.md
+++ b/tips/TIP-0046/tip-0046.md
@@ -80,8 +80,11 @@ timestamp `Unix Timestamp` (in seconds) is calculated as follows:
 
 Each epoch has a corresponding epoch index, which is a `uint32`. To calculate the epoch index of a slot index, that is,
 the index of the epoch to which the slot belongs, the protocol parameter `Slots Per Epoch Exponent` is used. The epoch
-index of a slot index `Slot Index` is `Slot Index >> Slots Per Epoch Exponent`, where `>>` is the _zero-fill
-right-shift_ or _logical shift_ operation.
+index of a slot index `Slot Index` is calculated as follows:
+
+- If `Slot Index <= Genesis Slot` then the epoch index is `0`.
+- Otherwise the epoch index is `(Slot Index - Genesis Slot) >> Slots Per Epoch Exponent)`, where `>>` is the _zero-fill
+  right-shift_ or _logical shift_ operation.
 
 ## Slot Commitment