diff --git a/beacon_chain/fork_choice_rule/distributions.nim b/beacon_chain/fork_choice_rule/distributions.nim
index 20d6457f5..fb885da1a 100644
--- a/beacon_chain/fork_choice_rule/distributions.nim
+++ b/beacon_chain/fork_choice_rule/distributions.nim
@@ -12,8 +12,9 @@
 
 import math, random
 
-proc normal_distribution(mean = 0.0, std = 1.0): int =
+proc normal_distribution*(mean = 0.0, std = 1.0): int =
   ## Return an integer sampled from a normal distribution (gaussian)
+  ## ⚠ This is not thread-safe
   # Implementation via the Box-Muller method
   # See https://en.wikipedia.org/wiki/Box–Muller_transform
 
@@ -34,7 +35,6 @@ proc normal_distribution(mean = 0.0, std = 1.0): int =
   z1 = R * sin(2 * PI * u2)
   return int(z0 * std + mean)
 
-
 when isMainModule:
   import sequtils, stats, strformat