diff --git a/app/models/attachment.rb b/app/models/attachment.rb
index 25c1bf1bc87..6720cd18514 100644
--- a/app/models/attachment.rb
+++ b/app/models/attachment.rb
@@ -69,13 +69,17 @@ class Attachment < ApplicationRecord
   # Returns an URL if the attachment is stored in an external (fog) attachment storage
   # or nil otherwise.
   def external_url(expires_in: nil)
-    url = URI.parse file.download_url(content_disposition: content_disposition, expires_in: expires_in) # returns a path if local
+    url = URI.parse file.download_url(external_url_options) # returns a path if local
 
     url if url.host
   rescue URI::InvalidURIError
     nil
   end
 
+  def external_url_options(expires_in: nil)
+    { content_disposition: content_disposition(include_filename: false), expires_in: expires_in }
+  end
+
   def external_storage?
     !external_url.nil?
   end
@@ -89,10 +93,14 @@ class Attachment < ApplicationRecord
     container.respond_to?(:project) ? container.project : nil
   end
 
-  def content_disposition
-    # Do not use filename with attachment as this may break for Unicode files
-    # specifically when using S3 for attachments.
-    inlineable? ? "inline" : "attachment"
+  def content_disposition(include_filename: true)
+    return "inline" if inlineable?
+
+    if include_filename
+      "attachment; filename=#{attachment.filename}"
+    else
+      "attachment"
+    end
   end
 
   def visible?(user = User.current)
diff --git a/lib/api/helpers/attachment_renderer.rb b/lib/api/helpers/attachment_renderer.rb
index 08735cfe2a6..40d1d6ff08e 100644
--- a/lib/api/helpers/attachment_renderer.rb
+++ b/lib/api/helpers/attachment_renderer.rb
@@ -76,7 +76,7 @@ module API
 
       def send_attachment(attachment)
         content_type attachment.content_type
-        header['Content-Disposition'] = "#{attachment.content_disposition}; filename=#{attachment.filename}"
+        header['Content-Disposition'] = attachment.content_disposition
         env['api.format'] = :binary
         sendfile attachment.diskfile.path
       end
diff --git a/modules/bim/lib/open_project/bim/engine.rb b/modules/bim/lib/open_project/bim/engine.rb
index 1c1a6f8adcc..e94a680208a 100644
--- a/modules/bim/lib/open_project/bim/engine.rb
+++ b/modules/bim/lib/open_project/bim/engine.rb
@@ -97,7 +97,7 @@ module OpenProject::Bim
 
     assets %w(bim/logo_openproject_bim_big.png)
 
-    patches %i[WorkPackage Type Journal RootSeeder Project FogFileUploader]
+    patches %i[Attachment WorkPackage Type Journal RootSeeder Project FogFileUploader]
 
     patch_with_namespace :OpenProject, :CustomStyles, :ColorThemes
     patch_with_namespace :API, :V3, :Activities, :ActivityRepresenter
diff --git a/modules/bim/lib/open_project/bim/patches/attachment_patch.rb b/modules/bim/lib/open_project/bim/patches/attachment_patch.rb
new file mode 100644
index 00000000000..80e7c0c486e
--- /dev/null
+++ b/modules/bim/lib/open_project/bim/patches/attachment_patch.rb
@@ -0,0 +1,61 @@
+#-- copyright
+# OpenProject is an open source project management software.
+# Copyright (C) 2012-2021 the OpenProject GmbH
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License version 3.
+#
+# OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
+# Copyright (C) 2006-2013 Jean-Philippe Lang
+# Copyright (C) 2010-2013 the ChiliProject Team
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+#
+# See COPYRIGHT and LICENSE files for more details.
+#++
+
+module OpenProject::Bim::Patches::AttachmentPatch
+  def self.included(base) # :nodoc:
+    base.prepend InstanceMethods
+  end
+
+  module InstanceMethods
+    def external_url_options(expires_in: nil)
+      return super unless ifc_model?
+
+      super.merge content_disposition: ifc_content_disposition
+    end
+
+    def content_disposition(include_filename: true)
+      return super unless ifc_model? && include_filename
+      
+      ifc_content_disposition
+    end
+
+    def ifc_model?
+      container_type == Bim::IfcModels::IfcModel.name && container.present?
+    end
+
+    def ifc_content_disposition
+      "attachment; filename=#{ifc_file_name}"
+    end
+
+    def ifc_file_name
+      title = container.title.sub /\.ifc\Z/, ''
+
+      title.to_localized_slug(:en) + ".ifc"
+    end
+  end
+end