diff --git a/x/slashing/keys.go b/x/slashing/keys.go
index 1f84a285dd..183dfde60d 100644
--- a/x/slashing/keys.go
+++ b/x/slashing/keys.go
@@ -34,7 +34,8 @@ func GetValidatorSlashingPeriodPrefix(v sdk.ConsAddress) []byte {
 // stored by *Tendermint* address (not operator address) followed by start height
 func GetValidatorSlashingPeriodKey(v sdk.ConsAddress, startHeight int64) []byte {
 	b := make([]byte, 8)
-	binary.LittleEndian.PutUint64(b, uint64(startHeight))
+	// this needs to be height + 1 because the slashing period for genesis validators starts at height -1
+	binary.LittleEndian.PutUint64(b, uint64(startHeight+1))
 	return append(GetValidatorSlashingPeriodPrefix(v), b...)
 }