diff --git a/lib/container.ex b/lib/container.ex
index 38a329ff..002ec165 100644
--- a/lib/container.ex
+++ b/lib/container.ex
@@ -90,18 +90,30 @@ defmodule Testcontainers.Container do
   Adds a _port_ to be exposed on the _container_.
   """
   def with_exposed_port(%__MODULE__{} = config, port) when is_integer(port) do
-    filtered_ports = config.exposed_ports |> Enum.reject(fn p -> p == port end)
+    filtered_ports =
+      config.exposed_ports
+      |> Enum.reject(fn
+        {p, _} -> p == port
+        p -> p == port
+      end)
 
-    %__MODULE__{config | exposed_ports: [port | filtered_ports]}
+    %__MODULE__{config | exposed_ports: [{port, nil} | filtered_ports]}
   end
 
   @doc """
   Adds multiple _ports_ to be exposed on the _container_.
   """
   def with_exposed_ports(%__MODULE__{} = config, ports) when is_list(ports) do
-    filtered_ports = config.exposed_ports |> Enum.reject(fn port -> port in ports end)
+    filtered_ports =
+      config.exposed_ports
+      |> Enum.reject(fn
+        {p, _} -> p in ports
+        p -> p in ports
+      end)
+
+    new_ports = Enum.map(ports, fn port -> {port, nil} end)
 
-    %__MODULE__{config | exposed_ports: ports ++ filtered_ports}
+    %__MODULE__{config | exposed_ports: new_ports ++ filtered_ports}
   end
 
   @doc """
@@ -242,13 +254,10 @@ defmodule Testcontainers.Container do
   """
   def mapped_port(%__MODULE__{} = container, port) when is_number(port) do
     container.exposed_ports
-    |> Enum.filter(fn
-      {exposed_port, _} -> exposed_port == port
-      port -> port == port
+    |> Enum.find_value(nil, fn
+      {^port, host_port} -> host_port
+      _ -> nil
     end)
-    |> List.first({})
-    |> Tuple.to_list()
-    |> List.last()
   end
 
   @doc """
diff --git a/lib/docker/api.ex b/lib/docker/api.ex
index da22e1ea..ed4ee76f 100644
--- a/lib/docker/api.ex
+++ b/lib/docker/api.ex
@@ -224,7 +224,6 @@ defmodule Testcontainers.Docker.Api do
     container_config.exposed_ports
     |> Enum.map(fn
       {container_port, _host_port} -> {container_port, %{}}
-      port -> {port, %{}}
     end)
     |> Enum.into(%{})
   end
@@ -237,11 +236,11 @@ defmodule Testcontainers.Docker.Api do
   defp map_port_bindings(%Container{} = container_config) do
     container_config.exposed_ports
     |> Enum.map(fn
+      {container_port, host_port} when is_nil(host_port) ->
+        {container_port, [%{"HostIp" => "0.0.0.0", "HostPort" => ""}]}
+
       {container_port, host_port} ->
         {container_port, [%{"HostIp" => "0.0.0.0", "HostPort" => to_string(host_port)}]}
-
-      port ->
-        {port, [%{"HostIp" => "0.0.0.0", "HostPort" => ""}]}
     end)
     |> Enum.into(%{})
   end
diff --git a/test/container_test.exs b/test/container_test.exs
index 9240fad4..b08c8289 100644
--- a/test/container_test.exs
+++ b/test/container_test.exs
@@ -21,10 +21,10 @@ defmodule Testcontainers.ContainerTest do
       container2 = ContainerBuilder.build(Testcontainers.PostgresContainer.new())
 
       assert Testcontainers.Util.Hash.struct_to_hash(container1) ==
-               "2ac8f31c61b760b17176a9b9e51bd9d969eb26adadc9bf3db4cdcac69cfb065f"
+               "082851e217cae88e1684169a9759a6d702d012016054c14b23d192f7e2559c63"
 
       assert Testcontainers.Util.Hash.struct_to_hash(container2) ==
-               "2ac8f31c61b760b17176a9b9e51bd9d969eb26adadc9bf3db4cdcac69cfb065f"
+               "082851e217cae88e1684169a9759a6d702d012016054c14b23d192f7e2559c63"
     end
   end
 
@@ -34,7 +34,7 @@ defmodule Testcontainers.ContainerTest do
         Container.new("my-image")
         |> Container.with_exposed_port(80)
 
-      assert container.exposed_ports == [80]
+      assert container.exposed_ports == [{80, nil}]
     end
 
     test "removes duplicate exposed ports" do
@@ -43,7 +43,7 @@ defmodule Testcontainers.ContainerTest do
         |> Container.with_exposed_port(80)
         |> Container.with_exposed_port(80)
 
-      assert container.exposed_ports == [80]
+      assert container.exposed_ports == [{80, nil}]
     end
   end
 
@@ -53,7 +53,7 @@ defmodule Testcontainers.ContainerTest do
         Container.new("my-image")
         |> Container.with_exposed_ports([80, 443])
 
-      assert container.exposed_ports == [80, 443]
+      assert container.exposed_ports == [{80, nil}, {443, nil}]
     end
 
     test "removes duplicate exposed ports" do
@@ -62,7 +62,7 @@ defmodule Testcontainers.ContainerTest do
         |> Container.with_exposed_ports([80, 443])
         |> Container.with_exposed_ports([80])
 
-      assert container.exposed_ports == [80, 443]
+      assert container.exposed_ports == [{80, nil}, {443, nil}]
     end
   end
 
@@ -96,6 +96,11 @@ defmodule Testcontainers.ContainerTest do
       container = Container.new("my-image")
       assert Container.mapped_port(container, 80) == nil
     end
+
+    test "returns nil (and does not crash) if the exposed port is present but not mapped (integer)" do
+      container = Container.new("my-image") |> Container.with_exposed_port(80)
+      assert Container.mapped_port(container, 80) == nil
+    end
   end
 
   describe "with_network_mode/2" do