diff --git a/lib/philomena/bans/subnet.ex b/lib/philomena/bans/subnet.ex
index bf8b8533..45285748 100644
--- a/lib/philomena/bans/subnet.ex
+++ b/lib/philomena/bans/subnet.ex
@@ -42,7 +42,7 @@ defmodule Philomena.Bans.Subnet do
       changeset
       |> get_field(:specification)
       |> case do
-        %Postgrex.INET{address: {h1, h2, h3, h4, h5, h6, h7, h8}, netmask: 128} ->
+        %Postgrex.INET{address: {h1, h2, h3, h4, _h5, _h6, _h7, _h8}, netmask: 128} ->
           %Postgrex.INET{address: {h1, h2, h3, h4, 0, 0, 0, 0}, netmask: 64}
 
         val ->
diff --git a/lib/philomena/duplicate_reports/duplicate_report.ex b/lib/philomena/duplicate_reports/duplicate_report.ex
index 231e41c7..34dfbf4c 100644
--- a/lib/philomena/duplicate_reports/duplicate_report.ex
+++ b/lib/philomena/duplicate_reports/duplicate_report.ex
@@ -30,6 +30,7 @@ defmodule Philomena.DuplicateReports.DuplicateReport do
     |> cast(attrs, [:reason])
     |> put_assoc(:user, attribution[:user])
     |> validate_length(:reason, max: 250, count: :bytes)
+    |> validate_source_is_not_target()
   end
 
   def accept_changeset(duplicate_report, user) do
@@ -55,4 +56,14 @@ defmodule Philomena.DuplicateReports.DuplicateReport do
     |> put_change(:modifier_id, user.id)
     |> put_change(:state, "rejected")
   end
+
+  defp validate_source_is_not_target(changeset) do
+    source_id = get_field(changeset, :image_id)
+    target_id = get_field(changeset, :duplicate_of_image_id)
+
+    case source_id == target_id do
+      true  -> add_error(changeset, :image_id, "must be different from the target")
+      false -> changeset
+    end
+  end
 end