diff --git a/lib/trinity/sim_logger.ex b/lib/trinity/sim_logger.ex
index 81c700c..1272ec3 100644
--- a/lib/trinity/sim_logger.ex
+++ b/lib/trinity/sim_logger.ex
@@ -55,15 +55,20 @@ defmodule Trinity.SimLogger do
   defmacro debug(message) do
     key = simulation_key()
 
-    {:<<>>, _, elements} = message
     values =
-      Enum.reduce(elements, [], fn
-        {:"::", _, [{{:., _, [Kernel, :to_string]}, _, [value]}, {:binary, _, _}]}, acc ->
-          [value | acc]
-        _, acc ->
-          acc
-      end)
-      |> Enum.reverse()
+      case message do
+        {:<<>>, _, elements} ->
+          # Extract interpolated variables
+          Enum.reduce(elements, [], fn
+            {:"::", _, [{{:., _, [Kernel, :to_string]}, _, [value]}, {:binary, _, _}]}, acc -> [value | acc]
+            _, acc -> acc
+          end)
+          |> Enum.reverse()
+
+        string when is_binary(string) ->
+          # There are no interpolated variables
+          []
+      end
 
     %{module: module, line: line} = __CALLER__
     values_tuple = {:{}, [], [module, line | values]}
diff --git a/test/trinity_test.exs b/test/trinity_test.exs
index 7a9e54a..7978093 100644
--- a/test/trinity_test.exs
+++ b/test/trinity_test.exs
@@ -34,6 +34,8 @@ defmodule TrinityTest do
       }
       state = write_value(state, initial_count)
 
+      # Note: this intentionally tests a log message with no variables
+      SimLogger.debug "Init complete"
       {:ok, state}
     end