diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 620625754a..0fdcc0f0c8 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -754,8 +754,9 @@ func (s *bgMarkSignal) clear() {
 }
 
 var work struct {
-	full    uint64                // lock-free list of full blocks workbuf
-	empty   uint64                // lock-free list of empty blocks workbuf
+	full  uint64 // lock-free list of full blocks workbuf
+	empty uint64 // lock-free list of empty blocks workbuf
+	// TODO(rlh): partial no longer used, remove. (issue #11922)
 	partial uint64                // lock-free list of partially filled blocks workbuf
 	pad0    [_CacheLineSize]uint8 // prevents false-sharing between full/empty and nproc/nwait
 	nproc   uint32
diff --git a/src/runtime/mgcwork.go b/src/runtime/mgcwork.go
index 4a1455c860..b18eaafba8 100644
--- a/src/runtime/mgcwork.go
+++ b/src/runtime/mgcwork.go
@@ -153,10 +153,18 @@ func (ww *gcWork) get() uintptr {
 }
 
 // dispose returns any cached pointers to the global queue.
+// The buffers are being put on the full queue so that the
+// write barriers will not simply reacquire them before the
+// GC can inspect them. This helps reduce the mutator's
+// ability to hide pointers during the concurrent mark phase.
+//
 //go:nowritebarrier
 func (w *gcWork) dispose() {
 	if wbuf := w.wbuf; wbuf != 0 {
-		putpartial(wbuf.ptr(), 167)
+		if wbuf.ptr().nobj == 0 {
+			throw("dispose: workbuf is empty")
+		}
+		putfull(wbuf.ptr(), 166)
 		w.wbuf = 0
 	}
 	if w.bytesMarked != 0 {