diff --git a/lib/ex_unit/lib/ex_unit/doc_test.ex b/lib/ex_unit/lib/ex_unit/doc_test.ex
index ab2c7128e14..e248004d9eb 100644
--- a/lib/ex_unit/lib/ex_unit/doc_test.ex
+++ b/lib/ex_unit/lib/ex_unit/doc_test.ex
@@ -428,7 +428,7 @@ defmodule ExUnit.DocTest do
   defp extract_tests(line_no, doc, module) do
     all_lines = String.split(doc, ~r/\n/, trim: false)
     lines = adjust_indent(all_lines, line_no + 1, module)
-    extract_tests(lines, "", "", [], true)
+    extract_tests(lines, "", "", [], true, module)
   end
 
   @iex_prompt ["iex>", "iex("]
@@ -451,7 +451,8 @@ defmodule ExUnit.DocTest do
     end
   end
 
-  defp adjust_indent(kind, [line | rest], line_no, adjusted_lines, indent, module) when kind in [:prompt, :after_prompt] do
+  defp adjust_indent(kind, [line | rest], line_no, adjusted_lines, indent, module)
+       when kind in [:prompt, :after_prompt] do
     stripped_line = strip_indent(line, indent)
 
     case String.trim_leading(line) do
@@ -511,91 +512,104 @@ defmodule ExUnit.DocTest do
 
   @fences ["```", "~~~"]
 
-  defp extract_tests([], "", "", [], _) do
+  defp extract_tests(lines, expr_acc, expected_acc, acc, new_test, module)
+  defp extract_tests([], "", "", [], _, _) do
     []
   end
 
-  defp extract_tests([], "", "", acc, _) do
+  defp extract_tests([], "", "", acc, _, _) do
     Enum.reverse(acc)
   end
 
   # End of input and we've still got a test pending.
-  defp extract_tests([], expr_acc, expected_acc, [test | t], _) do
+  defp extract_tests([], expr_acc, expected_acc, [test | rest], _, _) do
     test = add_expr(test, expr_acc, expected_acc)
-    Enum.reverse([test | t])
+    Enum.reverse([test | rest])
   end
 
   # We've encountered the next test on an adjacent line. Put them into one group.
-  defp extract_tests([{"iex>" <> _, _} | _] = list, expr_acc, expected_acc,
-                     [test | t], newtest) when expr_acc != "" and expected_acc != "" do
+  defp extract_tests([{"iex>" <> _, _} | _] = list, expr_acc, expected_acc, [test | rest], new_test, module)
+       when expr_acc != "" and expected_acc != "" do
     test = add_expr(test, expr_acc, expected_acc)
-    extract_tests(list, "", "", [test | t], newtest)
+    extract_tests(list, "", "", [test | rest], new_test, module)
   end
 
   # Store expr_acc and start a new test case.
-  defp extract_tests([{"iex>" <> string, line} | lines], "", expected_acc, acc, true) do
-    test = %{line: line, fun_arity: nil, exprs: []}
-    extract_tests(lines, string, expected_acc, [test | acc], false)
+  defp extract_tests([{"iex>" <> string, line_no} | lines], "", expected_acc, acc, true, module) do
+    test = %{line: line_no, fun_arity: nil, exprs: []}
+    extract_tests(lines, string, expected_acc, [test | acc], false, module)
   end
 
   # Store expr_acc.
-  defp extract_tests([{"iex>" <> string, _} | lines], "", expected_acc, acc, false) do
-    extract_tests(lines, string, expected_acc, acc, false)
+  defp extract_tests([{"iex>" <> string, _} | lines], "", expected_acc, acc, false, module) do
+    extract_tests(lines, string, expected_acc, acc, false, module)
   end
 
   # Still gathering expr_acc. Synonym for the next clause.
-  defp extract_tests([{"iex>" <> string, _} | lines], expr_acc, expected_acc, acc, newtest) do
-    extract_tests(lines, expr_acc <> "\n" <> string, expected_acc, acc, newtest)
+  defp extract_tests([{"iex>" <> string, _} | lines], expr_acc, expected_acc, acc, new_test, module) do
+    extract_tests(lines, expr_acc <> "\n" <> string, expected_acc, acc, new_test, module)
   end
 
   # Still gathering expr_acc. Synonym for the previous clause.
-  defp extract_tests([{"...>" <> string, _} | lines], expr_acc, expected_acc, acc, newtest) when expr_acc != "" do
-    extract_tests(lines, expr_acc <> "\n" <> string, expected_acc, acc, newtest)
+  defp extract_tests([{"...>" <> string, _} | lines], expr_acc, expected_acc, acc, new_test, module)
+       when expr_acc != "" do
+    extract_tests(lines, expr_acc <> "\n" <> string, expected_acc, acc, new_test, module)
   end
 
   # Expression numbers are simply skipped.
-  defp extract_tests([{<<"iex(", _>> <> string, line} | lines], expr_acc, expected_acc, acc, newtest) do
-    extract_tests([{"iex" <> skip_iex_number(string), line} | lines], expr_acc, expected_acc, acc, newtest)
+  defp extract_tests([{<<"iex(", _>> <> string = line, line_no} | lines],
+                     expr_acc, expected_acc, acc, new_test, module) do
+    extract_tests([{"iex" <> skip_iex_number(string, module, line_no, line), line_no} | lines],
+                     expr_acc, expected_acc, acc, new_test, module)
   end
 
   # Expression numbers are simply skipped redux.
-  defp extract_tests([{<<"...(", _>> <> string, line} | lines], expr_acc, expected_acc, acc, newtest) do
-    extract_tests([{"..." <> skip_iex_number(string), line} | lines], expr_acc, expected_acc, acc, newtest)
+  defp extract_tests([{<<"...(", _>> <> string, line_no} = line | lines],
+                     expr_acc, expected_acc, acc, new_test, module) do
+    extract_tests([{"..." <> skip_iex_number(string, module, line_no, line), line_no} | lines],
+                  expr_acc, expected_acc, acc, new_test, module)
   end
 
   # Skip empty or documentation line.
-  defp extract_tests([_ | lines], "", "", acc, _) do
-    extract_tests(lines, "", "", acc, true)
+  defp extract_tests([_ | lines], "", "", acc, _, module) do
+    extract_tests(lines, "", "", acc, true, module)
   end
 
   # Encountered end of fenced code block, store pending test
-  defp extract_tests([{<<fence::3-bytes>> <> _, _} | lines], expr_acc, expected_acc, [test | t], _)
-      when fence in @fences and expr_acc != "" do
+  defp extract_tests([{<<fence::3-bytes>> <> _, _} | lines], expr_acc, expected_acc,
+                     [test | rest], _new_test, module)
+       when fence in @fences and expr_acc != "" do
     test = add_expr(test, expr_acc, expected_acc)
-    extract_tests(lines, "", "", [test | t], true)
+    extract_tests(lines, "", "", [test | rest], true, module)
   end
 
   # Encountered an empty line, store pending test
-  defp extract_tests([{"", _} | lines], expr_acc, expected_acc, [test | t], _) do
+  defp extract_tests([{"", _} | lines], expr_acc, expected_acc, [test | rest], _new_test, module) do
     test = add_expr(test, expr_acc, expected_acc)
-    extract_tests(lines, "", "", [test | t], true)
+    extract_tests(lines, "", "", [test | rest], true, module)
   end
 
   # Finally, parse expected_acc.
-  defp extract_tests([{expected, _} | lines], expr_acc, "", acc, newtest) do
-    extract_tests(lines, expr_acc, expected, acc, newtest)
+  defp extract_tests([{expected, _} | lines], expr_acc, "", acc, new_test, module) do
+    extract_tests(lines, expr_acc, expected, acc, new_test, module)
   end
 
-  defp extract_tests([{expected, _} | lines], expr_acc, expected_acc, acc, newtest) do
-    extract_tests(lines, expr_acc, expected_acc <> "\n" <> expected, acc, newtest)
+  defp extract_tests([{expected, _} | lines], expr_acc, expected_acc, acc, new_test, module) do
+    extract_tests(lines, expr_acc, expected_acc <> "\n" <> expected, acc, new_test, module)
   end
 
-  defp skip_iex_number(")>" <> string) do
+  defp skip_iex_number(")>" <> string, _module, _line_no, _line) do
     ">" <> string
   end
 
-  defp skip_iex_number(<<_>> <> string) do
-    skip_iex_number(string)
+  defp skip_iex_number("", module, line_no, line) do
+    message =
+      "unknown IEx prompt: #{inspect line}.\nAccepted formats are: iex>, iex(1)>, ...>, ...(1)>}"
+    raise Error, line: line_no, module: module, message: message
+  end
+
+  defp skip_iex_number(<<_>> <> string, module, line_no, line) do
+    skip_iex_number(string, module, line_no, line)
   end
 
   defp normalize_test(%{exprs: exprs} = test, fa) do
diff --git a/lib/ex_unit/test/ex_unit/doc_test_test.exs b/lib/ex_unit/test/ex_unit/doc_test_test.exs
index 30a1dc727b5..4a11d6d2919 100644
--- a/lib/ex_unit/test/ex_unit/doc_test_test.exs
+++ b/lib/ex_unit/test/ex_unit/doc_test_test.exs
@@ -280,6 +280,15 @@ defmodule ExUnit.DocTestTest.Numbered do
   def test_fun(), do: :ok
 end |> write_beam()
 
+defmodule ExUnit.DocTestTest.Host do
+  @doc """
+      iex(foo@bar)1> 1 +
+      ...(foo@bar)1> 2
+      3
+  """
+  def test_fun(), do: :ok
+end |> write_beam()
+
 defmodule ExUnit.DocTestTest.Haiku do
   @moduledoc """
   This module describes the ancient Japanese poem form known as Haiku.
@@ -373,7 +382,7 @@ defmodule ExUnit.DocTestTest do
   test "doctest failures" do
     # When adding or removing lines above this line, the tests below will
     # fail because we are explicitly asserting some doctest lines from
-    # ActuallyCompiled in the format of test/ex_unit/doc_test_test.exs:<LINE>.
+    # ActuallyCompiled in the format of "test/ex_unit/doc_test_test.exs:<LINE>".
     defmodule ActuallyCompiled do
       use ExUnit.Case
       doctest ExUnit.DocTestTest.Invalid
@@ -388,7 +397,7 @@ defmodule ExUnit.DocTestTest do
 
     assert output =~ """
       1) test moduledoc at ExUnit.DocTestTest.Invalid (1) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:379
+         test/ex_unit/doc_test_test.exs:388
          Doctest did not compile, got: (SyntaxError) test/ex_unit/doc_test_test.exs:127: syntax error before: '*'
          code: 1 + * 1
          stacktrace:
@@ -397,7 +406,7 @@ defmodule ExUnit.DocTestTest do
 
     assert output =~ """
       2) test moduledoc at ExUnit.DocTestTest.Invalid (2) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:379
+         test/ex_unit/doc_test_test.exs:388
          Doctest failed
          code: 1 + hd(List.flatten([1])) === 3
          left: 2
@@ -407,7 +416,7 @@ defmodule ExUnit.DocTestTest do
 
     assert output =~ """
       3) test moduledoc at ExUnit.DocTestTest.Invalid (3) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:379
+         test/ex_unit/doc_test_test.exs:388
          Doctest failed
          code: inspect(:oops) === "#MapSet<[]>"
          left: ":oops"
@@ -418,7 +427,7 @@ defmodule ExUnit.DocTestTest do
     # The stacktrace points to the cause of the error
     assert output =~ """
       4) test moduledoc at ExUnit.DocTestTest.Invalid (4) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:379
+         test/ex_unit/doc_test_test.exs:388
          Doctest failed: got UndefinedFunctionError with message "function Hello.world/0 is undefined (module Hello is not available)"
          code: Hello.world
          stacktrace:
@@ -428,7 +437,7 @@ defmodule ExUnit.DocTestTest do
 
     assert output =~ """
       5) test moduledoc at ExUnit.DocTestTest.Invalid (5) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:379
+         test/ex_unit/doc_test_test.exs:388
          Doctest failed: expected exception WhatIsThis but got RuntimeError with message "oops"
          code: raise "oops"
          stacktrace:
@@ -437,7 +446,7 @@ defmodule ExUnit.DocTestTest do
 
     assert output =~ """
       6) test moduledoc at ExUnit.DocTestTest.Invalid (6) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:379
+         test/ex_unit/doc_test_test.exs:388
          Doctest failed: wrong message for RuntimeError
          expected:
            "hello"
@@ -450,7 +459,7 @@ defmodule ExUnit.DocTestTest do
 
     assert output =~ """
       7) test doc at ExUnit.DocTestTest.Invalid.a/0 (7) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:379
+         test/ex_unit/doc_test_test.exs:388
          Doctest did not compile, got: (SyntaxError) test/ex_unit/doc_test_test.exs:148: syntax error before: '*'
          code: 1 + * 1
          stacktrace:
@@ -459,7 +468,7 @@ defmodule ExUnit.DocTestTest do
 
     assert output =~ """
       8) test doc at ExUnit.DocTestTest.Invalid.b/0 (8) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:379
+         test/ex_unit/doc_test_test.exs:388
          Doctest did not compile, got: (SyntaxError) test/ex_unit/doc_test_test.exs:154: syntax error before: '*'
          code: 1 + * 1
          stacktrace:
@@ -468,7 +477,7 @@ defmodule ExUnit.DocTestTest do
 
     assert output =~ """
       9) test doc at ExUnit.DocTestTest.Invalid.dedented_past_fence/0 (9) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:379
+         test/ex_unit/doc_test_test.exs:388
          Doctest did not compile, got: (SyntaxError) test/ex_unit/doc_test_test.exs:178: unexpected token: "`" (column 5, codepoint U+0060)
          code: 3
                    ```
@@ -478,7 +487,7 @@ defmodule ExUnit.DocTestTest do
 
     assert output =~ """
      10) test doc at ExUnit.DocTestTest.Invalid.indented_not_enough/0 (10) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:379
+         test/ex_unit/doc_test_test.exs:388
          Doctest did not compile, got: (SyntaxError) test/ex_unit/doc_test_test.exs:162: unexpected token: "`" (column 1, codepoint U+0060)
          code: 3
                `
@@ -488,7 +497,7 @@ defmodule ExUnit.DocTestTest do
 
     assert output =~ """
      11) test doc at ExUnit.DocTestTest.Invalid.indented_too_much/0 (11) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:379
+         test/ex_unit/doc_test_test.exs:388
          Doctest did not compile, got: (SyntaxError) test/ex_unit/doc_test_test.exs:170: unexpected token: "`" (column 3, codepoint U+0060)
          code: 3
                  ```
@@ -497,7 +506,7 @@ defmodule ExUnit.DocTestTest do
     """
   end
 
-  test "iex prefix contains a number" do
+  test "IEx prefix contains a number" do
     defmodule NumberedUsage do
       use ExUnit.Case
       doctest ExUnit.DocTestTest.Numbered
@@ -507,6 +516,20 @@ defmodule ExUnit.DocTestTest do
     assert capture_io(fn -> ExUnit.run end) =~ "1 test, 0 failures"
   end
 
+  test "IEx prompt contains host" do
+    message =
+      ~s[unknown IEx prompt: "iex(foo@bar)1> 1 +".\nAccepted formats are: iex>, iex(1)>, ...>, ...(1)>]
+
+    regex = ~r[test/ex_unit/doc_test_test\.exs:\d+: #{Regex.escape(message)}]
+
+    assert_raise ExUnit.DocTest.Error, regex, fn ->
+      defmodule HostUsage do
+        use ExUnit.Case
+        doctest ExUnit.DocTestTest.Host
+      end
+    end
+  end
+
   test "tags tests as doctests" do
     defmodule DoctestTag do
       use ExUnit.Case
@@ -532,7 +555,7 @@ defmodule ExUnit.DocTestTest do
   end
 
   test "fails on invalid module" do
-    assert_raise CompileError, ~r"module ExUnit.DocTestTest.Unknown is not loaded and could not be found", fn ->
+    assert_raise CompileError, ~r"module ExUnit\.DocTestTest\.Unknown is not loaded and could not be found", fn ->
       defmodule NeverCompiled do
         import ExUnit.DocTest
         doctest ExUnit.DocTestTest.Unknown
@@ -541,7 +564,7 @@ defmodule ExUnit.DocTestTest do
   end
 
   test "fails when there are no docs" do
-    assert_raise ExUnit.DocTest.Error, ~r"could not retrieve the documentation for module ExUnit.DocTestTest", fn ->
+    assert_raise ExUnit.DocTest.Error, ~r"could not retrieve the documentation for module ExUnit\.DocTestTest", fn ->
       defmodule NeverCompiled do
         import ExUnit.DocTest
         doctest ExUnit.DocTestTest
@@ -551,7 +574,7 @@ defmodule ExUnit.DocTestTest do
 
   test "fails in indentation mismatch" do
     assert_raise ExUnit.DocTest.Error,
-      ~r[test/ex_unit/doc_test_test.exs:\d+: indentation level mismatch: "   iex> bar = 2", should have been 2 spaces], fn ->
+      ~r[test/ex_unit/doc_test_test\.exs:\d+: indentation level mismatch: "   iex> bar = 2", should have been 2 spaces], fn ->
       defmodule NeverCompiled do
         import ExUnit.DocTest
         doctest ExUnit.DocTestTest.IndentationMismatchedPrompt
@@ -559,7 +582,7 @@ defmodule ExUnit.DocTestTest do
     end
 
     assert_raise ExUnit.DocTest.Error,
-      ~r[test/ex_unit/doc_test_test.exs:\d+: indentation level mismatch: "    3", should have been 2 spaces], fn ->
+      ~r[test/ex_unit/doc_test_test\.exs:\d+: indentation level mismatch: "    3", should have been 2 spaces], fn ->
       defmodule NeverCompiled do
         import ExUnit.DocTest
         doctest ExUnit.DocTestTest.IndentationTooMuch
@@ -567,7 +590,7 @@ defmodule ExUnit.DocTestTest do
     end
 
     assert_raise ExUnit.DocTest.Error,
-      ~r[test/ex_unit/doc_test_test.exs:\d+: indentation level mismatch: \"  3\", should have been 4 spaces], fn ->
+      ~r[test/ex_unit/doc_test_test\.exs:\d+: indentation level mismatch: \"  3\", should have been 4 spaces], fn ->
       defmodule NeverCompiled do
         import ExUnit.DocTest
         doctest ExUnit.DocTestTest.IndentationNotEnough
@@ -577,7 +600,7 @@ defmodule ExUnit.DocTestTest do
 
   test "fails with improper termination" do
     assert_raise ExUnit.DocTest.Error,
-      ~r[test/ex_unit/doc_test_test.exs:\d+: expected non-blank line to follow iex> prompt], fn ->
+      ~r[test/ex_unit/doc_test_test\.exs:\d+: expected non-blank line to follow iex> prompt], fn ->
       defmodule NeverCompiled do
         import ExUnit.DocTest
         doctest ExUnit.DocTestTest.Incomplete