diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index f2e7f707ed..6e56b4b1d1 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -3306,7 +3306,7 @@ func newproc1(fn *funcval, argp *uint8, narg int32, callergp *g, callerpc uintpt
 			if stkmap.nbit > 0 {
 				// We're in the prologue, so it's always stack map index 0.
 				bv := stackmapdata(stkmap, 0)
-				bulkBarrierBitmap(spArg, spArg, uintptr(narg), 0, bv.bytedata)
+				bulkBarrierBitmap(spArg, spArg, uintptr(bv.n)*sys.PtrSize, 0, bv.bytedata)
 			}
 		}
 	}
diff --git a/test/fixedbugs/issue29362b.go b/test/fixedbugs/issue29362b.go
new file mode 100644
index 0000000000..d1e3b4733f
--- /dev/null
+++ b/test/fixedbugs/issue29362b.go
@@ -0,0 +1,53 @@
+// run
+
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Verify that we don't consider a Go'd function's
+// arguments as pointers when they aren't.
+
+package main
+
+import (
+	"unsafe"
+)
+
+var badPtr uintptr
+
+var sink []byte
+
+func init() {
+	// Allocate large enough to use largeAlloc.
+	b := make([]byte, 1<<16-1)
+	sink = b // force heap allocation
+	//  Any space between the object and the end of page is invalid to point to.
+	badPtr = uintptr(unsafe.Pointer(&b[len(b)-1])) + 1
+}
+
+var throttle = make(chan struct{}, 10)
+
+// There are 2 arg bitmaps for this function, each with 2 bits.
+// In the first, p and q are both live, so that bitmap is 11.
+// In the second, only p is live, so that bitmap is 10.
+// Bitmaps are byte aligned, so if the first bitmap is interpreted as
+// extending across the entire argument area, we incorrectly concatenate
+// the bitmaps and end up using 110000001. That bad bitmap causes a6
+// to be considered a pointer.
+func noPointerArgs(p, q *byte, a0, a1, a2, a3, a4, a5, a6 uintptr) {
+	sink = make([]byte, 4096)
+	sinkptr = q
+	<-throttle
+	sinkptr = p
+}
+
+var sinkptr *byte
+
+func main() {
+	const N = 1000
+	for i := 0; i < N; i++ {
+		throttle <- struct{}{}
+		go noPointerArgs(nil, nil, badPtr, badPtr, badPtr, badPtr, badPtr, badPtr, badPtr)
+		sink = make([]byte, 4096)
+	}
+}