diff --git a/internal/pipewire/pod.go b/internal/pipewire/pod.go
index 15ff25c..d851cb1 100644
--- a/internal/pipewire/pod.go
+++ b/internal/pipewire/pod.go
@@ -505,7 +505,8 @@ type SPADict []SPADictItem
 // Size satisfies [KnownSize] with a value computed at runtime.
 func (d *SPADict) Size() Word {
 	if d == nil {
-		return 0
+		// None type prefix with zero-length body
+		return SizePrefix
 	}
 
 	// struct prefix, NItems value