diff --git a/beacon_chain/spec/datatypes/base.nim b/beacon_chain/spec/datatypes/base.nim
index 88c56f7574..c75e869e28 100644
--- a/beacon_chain/spec/datatypes/base.nim
+++ b/beacon_chain/spec/datatypes/base.nim
@@ -623,13 +623,10 @@ proc readValue*(reader: var JsonReader, value: var ForkDigest)
 static: doAssert high(int) >= high(int32)
 
 # `ValidatorIndex` seq handling.
-template `[]`*[T](a: var seq[T], b: ValidatorIndex): var T =
-  a[b.int]
-
 template `[]=`*[T](a: var seq[T], b: ValidatorIndex, c: T) =
   a[b.int] = c
 
-template `[]`*[T](a: seq[T], b: ValidatorIndex): auto =
+template `[]`*[T](a: seq[T], b: ValidatorIndex): auto = # Also var seq (!)
   a[b.int]
 
 # `ValidatorIndex` Nim integration