diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0972fe8..f4e881c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - More presets from Reaby, and all new and existing presets were normalized
   roughly to -12 dBFS true peak. ([#211][i211])
 
+### Fixed
+- The tracker thought that "sync" unit pops the value from stack, even if the VM
+  did not, resulting it claiming errors in patches that worked once compiled.
+
 ## [0.5.0]
 ### BREAKING CHANGES
 - BREAKING CHANGE: always first modulate delay time, then apply notetracking. In
diff --git a/patch.go b/patch.go
index 8268d25..a7bca4b 100644
--- a/patch.go
+++ b/patch.go
@@ -426,7 +426,7 @@ var stackUseMonoStereo = map[string][2]StackUse{
 		{},
 	},
 	"sync": {
-		{Inputs: [][]int{{0}}, Modifies: []bool{false}, NumOutputs: 0},
+		{Inputs: [][]int{{0}}, Modifies: []bool{false}, NumOutputs: 1},
 		{},
 	},
 }