diff --git a/src/runtime/mgcsweep.go b/src/runtime/mgcsweep.go
index 104bd868faf..b7528ab68f1 100644
--- a/src/runtime/mgcsweep.go
+++ b/src/runtime/mgcsweep.go
@@ -101,7 +101,7 @@ func sweepone() uintptr {
 			// This can happen if direct sweeping already
 			// swept this span, but in that case the sweep
 			// generation should always be up-to-date.
-			if s.sweepgen != sg {
+			if !(s.sweepgen == sg || s.sweepgen == sg+3) {
 				print("runtime: bad span s.state=", s.state, " s.sweepgen=", s.sweepgen, " sweepgen=", sg, "\n")
 				throw("non in-use span in unswept list")
 			}