diff --git a/lib/polymorphic_embed.ex b/lib/polymorphic_embed.ex
index 7e64891..3f631f2 100644
--- a/lib/polymorphic_embed.ex
+++ b/lib/polymorphic_embed.ex
@@ -278,8 +278,12 @@ defmodule PolymorphicEmbed do
 
           module ->
             data_for_field =
-              Enum.find(list_data_for_field, fn datum ->
-                datum.id != nil and datum.id == params[:id] and datum.__struct__ == module
+              Enum.find(list_data_for_field, fn
+                %{id: id} = datum when not is_nil(id) ->
+                  id == params[:id] and datum.__struct__ == module
+
+                _ ->
+                  nil
               end)
 
             embed_changeset =
diff --git a/test/polymorphic_embed_test.exs b/test/polymorphic_embed_test.exs
index d658271..f36bd60 100644
--- a/test/polymorphic_embed_test.exs
+++ b/test/polymorphic_embed_test.exs
@@ -1203,6 +1203,18 @@ defmodule PolymorphicEmbedTest do
             age: "aquarius",
             address: "address"
           }
+        ],
+        contexts3: [
+          %{
+            __type__: "device",
+            ref: "12345",
+            type: "cellphone"
+          },
+          %{
+            __type__: "device",
+            ref: "56789",
+            type: "laptop"
+          }
         ]
       }
 
@@ -1212,7 +1224,11 @@ defmodule PolymorphicEmbedTest do
         |> Repo.insert!()
 
       Enum.each(reminder.contexts, fn context ->
-        assert context.id
+        assert Map.has_key?(context, :id)
+      end)
+
+      Enum.each(reminder.contexts3, fn context ->
+        refute Map.has_key?(context, :id)
       end)
 
       reminder =
@@ -1223,7 +1239,7 @@ defmodule PolymorphicEmbedTest do
       assert reminder.contexts |> length() == 2
 
       Enum.each(reminder.contexts, fn context ->
-        assert context.id
+        assert Map.has_key?(context, :id)
       end)
 
       if polymorphic?(generator) do
@@ -1286,6 +1302,27 @@ defmodule PolymorphicEmbedTest do
 
       assert Enum.at(reminder.contexts, 0).id == Enum.at(updated_reminder.contexts, 0).id
       assert Enum.at(reminder.contexts, 1).id != Enum.at(updated_reminder.contexts, 1).id
+
+      # Make sure it also works for embeds without ids (`@primary_key false`)
+      attrs = %{
+        contexts3: [
+          %{
+            __type__: "device",
+            ref: "12345",
+            type: "cellphone"
+          },
+          %{
+            __type__: "device",
+            ref: "56789",
+            type: "laptop"
+          }
+        ]
+      }
+
+      assert {:ok, _} =
+               reminder
+               |> reminder_module.changeset(attrs)
+               |> Repo.update()
     end
   end
 
diff --git a/test/support/migrations/20000101000000_create_tables.exs b/test/support/migrations/20000101000000_create_tables.exs
index e1167f9..c43cda7 100644
--- a/test/support/migrations/20000101000000_create_tables.exs
+++ b/test/support/migrations/20000101000000_create_tables.exs
@@ -11,6 +11,7 @@ defmodule PolymorphicEmbed.CreateTables do
       add(:channel3, :map)
       add(:contexts, :map)
       add(:contexts2, :map)
+      add(:contexts3, :map)
 
       timestamps()
     end
diff --git a/test/support/models/not_polymorphic/reminder.ex b/test/support/models/not_polymorphic/reminder.ex
index cdbae77..03c596a 100644
--- a/test/support/models/not_polymorphic/reminder.ex
+++ b/test/support/models/not_polymorphic/reminder.ex
@@ -13,6 +13,10 @@ defmodule PolymorphicEmbed.Regular.Reminder do
       on_replace: :delete
     )
 
+    embeds_many(:contexts3, PolymorphicEmbed.Regular.Reminder.Context.DeviceNoId,
+      on_replace: :delete
+    )
+
     timestamps()
   end
 
@@ -22,6 +26,7 @@ defmodule PolymorphicEmbed.Regular.Reminder do
     |> validate_required(:date)
     |> cast_embed(:channel)
     |> cast_embed(:contexts)
+    |> cast_embed(:contexts3)
   end
 
   def custom_changeset(struct, attrs) do
diff --git a/test/support/models/not_polymorphic/reminder/context/device_no_id.ex b/test/support/models/not_polymorphic/reminder/context/device_no_id.ex
new file mode 100644
index 0000000..d863796
--- /dev/null
+++ b/test/support/models/not_polymorphic/reminder/context/device_no_id.ex
@@ -0,0 +1,21 @@
+defmodule PolymorphicEmbed.Regular.Reminder.Context.DeviceNoId do
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  @primary_key false
+
+  embedded_schema do
+    field :ref, :string
+    field :type, :string
+
+    embeds_one :extra, Extra do
+      field :imei, :string
+    end
+  end
+
+  def changeset(struct, params) do
+    struct
+    |> cast(params, ~w(ref type)a)
+    |> validate_required(~w(type)a)
+  end
+end
diff --git a/test/support/models/polymorphic/reminder.ex b/test/support/models/polymorphic/reminder.ex
index a77efb0..632a378 100644
--- a/test/support/models/polymorphic/reminder.ex
+++ b/test/support/models/polymorphic/reminder.ex
@@ -56,6 +56,15 @@ defmodule PolymorphicEmbed.Reminder do
       on_replace: :delete
     )
 
+    polymorphic_embeds_many(:contexts3,
+      types: [
+        location: PolymorphicEmbed.Reminder.Context.Location,
+        age: PolymorphicEmbed.Reminder.Context.Age,
+        device: PolymorphicEmbed.Reminder.Context.DeviceNoId
+      ],
+      on_replace: :delete
+    )
+
     timestamps()
   end
 
@@ -66,6 +75,7 @@ defmodule PolymorphicEmbed.Reminder do
     |> cast_polymorphic_embed(:channel)
     |> cast_polymorphic_embed(:contexts)
     |> cast_polymorphic_embed(:contexts2)
+    |> cast_polymorphic_embed(:contexts3)
   end
 
   def custom_changeset(struct, values) do
diff --git a/test/support/models/polymorphic/reminder/context/device_no_id.ex b/test/support/models/polymorphic/reminder/context/device_no_id.ex
new file mode 100644
index 0000000..3f6f9a5
--- /dev/null
+++ b/test/support/models/polymorphic/reminder/context/device_no_id.ex
@@ -0,0 +1,21 @@
+defmodule PolymorphicEmbed.Reminder.Context.DeviceNoId do
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  @primary_key false
+
+  embedded_schema do
+    field :ref, :string
+    field :type, :string
+
+    embeds_one :extra, Extra do
+      field :imei, :string
+    end
+  end
+
+  def changeset(struct, params) do
+    struct
+    |> cast(params, ~w(ref type)a)
+    |> validate_required(~w(type)a)
+  end
+end