diff --git a/app/models/remote_theme.rb b/app/models/remote_theme.rb
index 10190ff064d..21f6bef275b 100644
--- a/app/models/remote_theme.rb
+++ b/app/models/remote_theme.rb
@@ -162,6 +162,11 @@ class RemoteTheme < ActiveRecord::Base
         new_path = "#{File.dirname(path)}/#{SecureRandom.hex}#{File.extname(path)}"
         File.rename(path, new_path) # OptimizedImage has strict file name restrictions, so rename temporarily
         upload = UploadCreator.new(File.open(new_path), File.basename(relative_path), for_theme: true).create_for(theme.user_id)
+
+        if !upload.errors.empty?
+          raise ImportError, I18n.t("themes.import_error.upload", name: name, errors: upload.errors.full_messages.join(","))
+        end
+
         updated_fields << theme.set_field(target: :common, name: name, type: :theme_upload_var, upload_id: upload.id)
       end
     end
diff --git a/config/locales/server.en.yml b/config/locales/server.en.yml
index daf859e9807..fe6edcf91b5 100644
--- a/config/locales/server.en.yml
+++ b/config/locales/server.en.yml
@@ -72,6 +72,7 @@ en:
       unrecognized_extension: "Unrecognized file extension: %{extension}"
     import_error:
       generic: An error occurred while importing that theme
+      upload: "Error creating upload asset: %{name}. %{errors}"
       about_json: "Import Error: about.json does not exist, or is invalid. Are you sure this is a Discourse Theme?"
       about_json_values: "about.json contains invalid values: %{errors}"
       modifier_values: "about.json modifiers contain invalid values: %{errors}"
diff --git a/spec/requests/admin/themes_controller_spec.rb b/spec/requests/admin/themes_controller_spec.rb
index 13f6d2499cf..90aa47d0fd9 100644
--- a/spec/requests/admin/themes_controller_spec.rb
+++ b/spec/requests/admin/themes_controller_spec.rb
@@ -151,6 +151,16 @@ describe Admin::ThemesController do
       expect(UserHistory.where(action: UserHistory.actions[:change_theme]).count).to eq(1)
     end
 
+    it 'fails to import with an error if uploads are not allowed' do
+      SiteSetting.theme_authorized_extensions = "nothing"
+
+      expect do
+        post "/admin/themes/import.json", params: { theme: theme_archive }
+      end.to change { Theme.count }.by (0)
+
+      expect(response.status).to eq(422)
+    end
+
     it 'imports a theme from an archive' do
       _existing_theme = Fabricate(:theme, name: "Header Icons")