diff --git a/NEWS b/NEWS
index d67bbb26a..d6bed1990 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,8 @@ ver 0.21.12 (not yet released)
 * decoder
   - opus: ignore case in replay gain tag names
   - opus, vorbis: decode the "end of stream" packet
+* output
+  - jack: fix mono-to-stereo conversion
 * Windows
   - support backslash in relative URIs loaded from playlists
 
diff --git a/src/output/plugins/JackOutputPlugin.cxx b/src/output/plugins/JackOutputPlugin.cxx
index f9535386e..6b82b8bf7 100644
--- a/src/output/plugins/JackOutputPlugin.cxx
+++ b/src/output/plugins/JackOutputPlugin.cxx
@@ -540,7 +540,7 @@ JackOutput::Start()
 		std::fill(dports + num_dports, dports + audio_format.channels,
 			  dports[0]);
 	} else if (num_dports > audio_format.channels) {
-		if (audio_format.channels == 1 && num_dports > 2) {
+		if (audio_format.channels == 1 && num_dports >= 2) {
 			/* mono input file: connect the one source
 			   channel to the both destination channels */
 			duplicate_port = dports[1];