diff --git a/lib/iex/lib/iex.ex b/lib/iex/lib/iex.ex
index 2a955d43458..e6a98066bda 100644
--- a/lib/iex/lib/iex.ex
+++ b/lib/iex/lib/iex.ex
@@ -785,7 +785,7 @@ defmodule IEx do
     __break__!(ast, module, fun, args, guards, stops, env)
   end
 
-  def __break__!(ast, _stops) do
+  def __break__!(ast, _stops, _env) do
     raise_unknown_break_ast!(ast)
   end
 
diff --git a/lib/iex/test/iex/helpers_test.exs b/lib/iex/test/iex/helpers_test.exs
index d8d64da379b..79e4b68dbe9 100644
--- a/lib/iex/test/iex/helpers_test.exs
+++ b/lib/iex/test/iex/helpers_test.exs
@@ -102,6 +102,12 @@ defmodule IEx.HelpersTest do
                    fn -> break!(PryExampleModule, :unknown, 2) end
     end
 
+    test "errors when setting up a break for unknown expression" do
+      assert_raise ArgumentError, ~r"unknown expression to break on", fn ->
+        break!(123)
+      end
+    end
+
     test "errors for non-Elixir modules" do
       assert_raise RuntimeError,
                    "could not set breakpoint, module :maps was not written in Elixir",