diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 48b42496965..78597da6417 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-0f6d673d5b1a3474c3424cb6994ae8ff9baed255
+838f926c93898767f0337122725a4f52a1335186
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/libgo/go/runtime/mwbbuf.go b/libgo/go/runtime/mwbbuf.go
index 4c875ff2d15..a27406e2987 100644
--- a/libgo/go/runtime/mwbbuf.go
+++ b/libgo/go/runtime/mwbbuf.go
@@ -285,10 +285,17 @@ func wbBufFlush1(_p_ *p) {
 			// path to reduce the rate of flushes?
 			continue
 		}
-		obj, span, objIndex := findObject(ptr, 0, 0, false)
+		obj, span, objIndex := findObject(ptr, 0, 0, !usestackmaps)
 		if obj == 0 {
 			continue
 		}
+		if span.isFree(objIndex) {
+			// For gccgo, it is possible that we have a write barrier
+			// writing to unintialized stack memory. So we could see
+			// a bad pointer in the write barrier buffer. Don't mark
+			// it in this case.
+			continue
+		}
 		// TODO: Consider making two passes where the first
 		// just prefetches the mark bits.
 		mbits := span.markBitsForIndex(objIndex)