diff --git a/libs/ardour/export_filename.cc b/libs/ardour/export_filename.cc
index 77dd9256f0..e8a4c6c493 100644
--- a/libs/ardour/export_filename.cc
+++ b/libs/ardour/export_filename.cc
@@ -187,6 +187,7 @@ ExportFilename::get_path (ExportFormatSpecPtr format) const
 			&& !include_revision
 			&& !include_timespan
 			&& !include_channel_config
+			&& !include_format_name
 			&& !include_channel
 			&& !include_date) {
 		with_timespan = true;
diff --git a/libs/ardour/export_handler.cc b/libs/ardour/export_handler.cc
index 759a5544d9..ebd19271b0 100644
--- a/libs/ardour/export_handler.cc
+++ b/libs/ardour/export_handler.cc
@@ -237,15 +237,19 @@ ExportHandler::handle_duplicate_format_extensions()
 
 	ExtCountMap counts;
 	for (ConfigMap::iterator it = timespan_bounds.first; it != timespan_bounds.second; ++it) {
+		std::string pfx;
+		if (it->second.filename->include_timespan) {
+			pfx = it->first->name();
+		}
 		if (it->second.filename->include_channel_config && it->second.channel_config) {
 			/* stem-export has multiple files in the same timestamp, but a different channel_config for each.
 			 * However channel_config is only set in ExportGraphBuilder::Encoder::init_writer()
 			 * so we cannot yet use   it->second.filename->get_path(it->second.format).
 			 * We have to explicily check uniqueness of "channel-config + extension" here:
 			 */
-			counts[it->second.channel_config->name() + it->second.format->extension()]++;
+			counts[pfx + it->second.channel_config->name() + it->second.format->extension()]++;
 		} else {
-			counts[it->second.format->extension()]++;
+			counts[pfx + it->second.format->extension()]++;
 		}
 	}
 
@@ -256,6 +260,7 @@ ExportHandler::handle_duplicate_format_extensions()
 
 	// Set this always, as the filenames are shared...
 	for (ConfigMap::iterator it = timespan_bounds.first; it != timespan_bounds.second; ++it) {
+		assert (it->second.filename->include_format_name == duplicates_found);
 		it->second.filename->include_format_name = duplicates_found;
 	}
 }
diff --git a/libs/ardour/export_profile_manager.cc b/libs/ardour/export_profile_manager.cc
index 0a0c3113fe..09c23cac19 100644
--- a/libs/ardour/export_profile_manager.cc
+++ b/libs/ardour/export_profile_manager.cc
@@ -888,6 +888,46 @@ ExportProfileManager::get_warnings ()
 
 	/*** Check files ***/
 
+	/* handle_duplicate_format_extensions */
+	for (TimespanList::iterator t1 = timespans->begin(); t1 != timespans->end(); ++t1) {
+
+		typedef std::map<std::string, int> ExtCountMap;
+		ExtCountMap counts;
+
+		FormatStateList::const_iterator format_it;
+		FilenameStateList::const_iterator filename_it;
+
+		for (format_it = formats.begin(), filename_it = filenames.begin();
+		     format_it != formats.end() && filename_it != filenames.end();
+		     ++format_it, ++filename_it) {
+
+			ExportFilenamePtr filename = (*filename_it)->filename;
+			filename->include_channel_config = (_type == StemExport) || (channel_configs.size() > 1);
+
+			for(ChannelConfigStateList::iterator cc_it = channel_configs.begin(); cc_it != channel_configs.end(); ++cc_it) {
+				if (filename->include_channel_config && (*cc_it)->config) {
+					counts[(*cc_it)->config->name() + (*format_it)->format->extension()]++;
+				} else {
+					counts[(*format_it)->format->extension()]++;
+				}
+			}
+		}
+
+		bool duplicates_found = false;
+		for (ExtCountMap::iterator it = counts.begin(); it != counts.end(); ++it) {
+			if (it->second > 1) {
+				duplicates_found = true;
+			}
+		}
+
+		for (format_it = formats.begin(), filename_it = filenames.begin();
+		     format_it != formats.end() && filename_it != filenames.end();
+		     ++format_it, ++filename_it) {
+			ExportFilenamePtr filename = (*filename_it)->filename;
+			filename->include_format_name = duplicates_found;
+		}
+	}
+
 	bool folder_ok = true;
 
 	if (channel_config_state) {