diff --git a/CHANGELOG.md b/CHANGELOG.md
index 309ab7f..36e8ab0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ### Fixed
 - In the WebAssembly core, $WRK was messed after stereo oscillators,
   making modulations not work
+- The Webassembly implementation of mono version of "out" unit
 
 ### Changed
 - The crush resolution is now in bits instead of linear range; this is a
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index cc917ba..897896d 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -65,6 +65,7 @@ endfunction(regression_test)
 
 regression_test(test_envelope "" ENVELOPE)
 regression_test(test_envelope_stereo ENVELOPE)
+regression_test(test_out ENVELOPE)
 regression_test(test_loadval "" LOADVAL)
 regression_test(test_loadval_stereo LOADVAL LOADVAL_STEREO)
 regression_test(test_gain LOADVAL GAIN)
diff --git a/tests/expected_output/test_out.raw b/tests/expected_output/test_out.raw
new file mode 100644
index 0000000..01ac885
Binary files /dev/null and b/tests/expected_output/test_out.raw differ
diff --git a/tests/test_out.yml b/tests/test_out.yml
new file mode 100644
index 0000000..a7cdf52
--- /dev/null
+++ b/tests/test_out.yml
@@ -0,0 +1,16 @@
+bpm: 100
+rowsperbeat: 4
+score:
+    rowsperpattern: 16
+    length: 1
+    tracks:
+        - numvoices: 1
+          order: [0]
+          patterns: [[64, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0]]
+patch:
+    - numvoices: 1
+      units:
+        - type: envelope
+          parameters: {attack: 64, decay: 64, gain: 64, release: 80, stereo: 0, sustain: 64}
+        - type: out
+          parameters: {gain: 128, stereo: 0}
diff --git a/vm/compiler/templates/wasm/sinks.wat b/vm/compiler/templates/wasm/sinks.wat
index 3e3c53a..fce3635 100644
--- a/vm/compiler/templates/wasm/sinks.wat
+++ b/vm/compiler/templates/wasm/sinks.wat
@@ -147,7 +147,11 @@
             (f32.load (local.get $ptr))
         )
     )
-    (local.set $ptr (i32.const {{add (index .Labels "su_globalports") 4}})) ;; synth.right, note that ATM does not seem to support mono ocpode at all
+    {{- if .StereoAndMono "out"}}
+    (if (local.get $stereo)(then
+    {{- end}}
+    {{- if .Stereo "out"}}
+    (local.set $ptr (i32.const {{add (index .Labels "su_globalports") 4}})) ;; synth.right
     (f32.store (local.get $ptr)
         (f32.add
             (f32.mul
@@ -157,6 +161,10 @@
             (f32.load (local.get $ptr))
         )
     )
+    {{- end}}
+    {{- if .StereoAndMono "out"}}
+    ))
+    {{- end}}
 )
 {{end}}