diff --git a/lib/trinity/sim_logger.ex b/lib/trinity/sim_logger.ex
index 834ff72..e61ebd0 100644
--- a/lib/trinity/sim_logger.ex
+++ b/lib/trinity/sim_logger.ex
@@ -12,6 +12,10 @@ defmodule Trinity.SimLogger do
 
   @spec log_head(non_neg_integer) :: [String.t]
   def log_head(count) do
+    %{log_atomic: log_atomic} = get_sim()
+    last_i = :atomics.get(log_atomic, 2)
+    count = min(last_i, count)
+
     scan_log(1, count)
   end
 
@@ -19,12 +23,17 @@ defmodule Trinity.SimLogger do
   def log_tail(count) do
     %{log_atomic: log_atomic} = get_sim()
     last_i = :atomics.get(log_atomic, 2)
+    count = min(last_i, count)
+
     scan_log(last_i - count, count)
   end
 
   @spec scan_log(non_neg_integer, non_neg_integer) :: [String.t]
   def scan_log(i, count) do
-    %{log: log} = get_sim()
+    %{log: log, log_atomic: log_atomic} = get_sim()
+    last_i = :atomics.get(log_atomic, 2)
+    count = min(last_i - i, count)
+
     do_scan_log(log, i + count, count, [])
   end