diff --git a/beacon_chain/spec/helpers.nim b/beacon_chain/spec/helpers.nim
index b7ee20a31..2092cd97f 100644
--- a/beacon_chain/spec/helpers.nim
+++ b/beacon_chain/spec/helpers.nim
@@ -49,11 +49,14 @@ func shortLog*(v: FinalityCheckpoints): auto =
 
 chronicles.formatIt FinalityCheckpoints: it.shortLog
 
-# https://github.com/ethereum/consensus-specs/blob/v1.4.0-beta.6/specs/phase0/beacon-chain.md#integer_squareroot
+# https://github.com/ethereum/consensus-specs/blob/v1.4.0-beta.7/specs/phase0/beacon-chain.md#integer_squareroot
 func integer_squareroot*(n: SomeInteger): SomeInteger =
   ## Return the largest integer ``x`` such that ``x**2 <= n``.
   doAssert n >= 0'u64
 
+  if n == high(uint64):
+    return 4294967295'u64
+
   var
     x = n
     y = (x + 1) div 2
diff --git a/tests/test_helpers.nim b/tests/test_helpers.nim
index 12dde955d..61693f7d7 100644
--- a/tests/test_helpers.nim
+++ b/tests/test_helpers.nim
@@ -21,13 +21,18 @@ import
 suite "Spec helpers":
   test "integer_squareroot":
     check:
-      integer_squareroot(0'u64) == 0'u64
       integer_squareroot(1'u64) == 1'u64
       integer_squareroot(2'u64) == 1'u64
       integer_squareroot(3'u64) == 1'u64
       integer_squareroot(4'u64) == 2'u64
       integer_squareroot(5'u64) == 2'u64
 
+      # https://github.com/ethereum/consensus-specs/pull/3600
+      integer_squareroot(0'u64) == 0'u64
+      integer_squareroot(100'u64) == 10'u64
+      integer_squareroot(18446744073709551614'u64) == 4294967295'u64
+      integer_squareroot(18446744073709551615'u64) == 4294967295'u64
+
   test "build_proof - BeaconState":
     var
       forked = newClone(initGenesisState())