diff --git a/misc/cgo/testsanitizers/msan.go b/misc/cgo/testsanitizers/msan.go
index 263fb5a2f7..ebfd5c3bd8 100644
--- a/misc/cgo/testsanitizers/msan.go
+++ b/misc/cgo/testsanitizers/msan.go
@@ -1,3 +1,7 @@
+// Copyright 2015 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.
+
 package main
 
 /*
diff --git a/misc/cgo/testsanitizers/msan2.go b/misc/cgo/testsanitizers/msan2.go
index d1da89c912..42dcd20c08 100644
--- a/misc/cgo/testsanitizers/msan2.go
+++ b/misc/cgo/testsanitizers/msan2.go
@@ -1,3 +1,7 @@
+// Copyright 2015 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.
+
 package main
 
 /*
diff --git a/misc/cgo/testsanitizers/msan4.go b/misc/cgo/testsanitizers/msan4.go
new file mode 100644
index 0000000000..c75e1c3486
--- /dev/null
+++ b/misc/cgo/testsanitizers/msan4.go
@@ -0,0 +1,50 @@
+// Copyright 2015 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.
+
+package main
+
+// The memory profiler can call copy from a slice on the system stack,
+// which msan used to think meant a reference to uninitialized memory.
+
+/*
+#include <time.h>
+#include <unistd.h>
+
+extern void Nop(char*);
+
+// Use weak as a hack to permit defining a function even though we use export.
+void poison() __attribute__ ((weak));
+
+// Poison the stack.
+void poison() {
+	char a[1024];
+	Nop(&a[0]);
+}
+
+*/
+import "C"
+
+import (
+	"runtime"
+)
+
+func main() {
+	runtime.MemProfileRate = 1
+	start(100)
+}
+
+func start(i int) {
+	if i == 0 {
+		return
+	}
+	C.poison()
+	// Tie up a thread.
+	// We won't actually wait for this sleep to complete.
+	go func() { C.sleep(1) }()
+	start(i - 1)
+}
+
+//export Nop
+func Nop(*C.char) {
+}
diff --git a/misc/cgo/testsanitizers/msan_fail.go b/misc/cgo/testsanitizers/msan_fail.go
index 50379a94d7..757e22c3da 100644
--- a/misc/cgo/testsanitizers/msan_fail.go
+++ b/misc/cgo/testsanitizers/msan_fail.go
@@ -1,3 +1,7 @@
+// Copyright 2015 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.
+
 package main
 
 /*
diff --git a/misc/cgo/testsanitizers/test.bash b/misc/cgo/testsanitizers/test.bash
index a4cff27701..0c28249c1b 100755
--- a/misc/cgo/testsanitizers/test.bash
+++ b/misc/cgo/testsanitizers/test.bash
@@ -57,6 +57,11 @@ if ! go run -msan msan3.go; then
   status=1
 fi
 
+if ! go run -msan msan4.go; then
+  echo "FAIL: msan4"
+  status=1
+fi
+
 if go run -msan msan_fail.go 2>/dev/null; then
   echo "FAIL: msan_fail"
   status=1
diff --git a/src/runtime/msan.go b/src/runtime/msan.go
index 7457fe1150..4dbdf05b21 100644
--- a/src/runtime/msan.go
+++ b/src/runtime/msan.go
@@ -23,8 +23,21 @@ func MSanWrite(addr unsafe.Pointer, len int) {
 // Private interface for the runtime.
 const msanenabled = true
 
+// If we are running on the system stack, the C program may have
+// marked part of that stack as uninitialized.  We don't instrument
+// the runtime, but operations like a slice copy can call msanread
+// anyhow for values on the stack.  Just ignore msanread when running
+// on the system stack.  The other msan functions are fine.
+func msanread(addr unsafe.Pointer, sz uintptr) {
+	g := getg()
+	if g == g.m.g0 || g == g.m.gsignal {
+		return
+	}
+	domsanread(addr, sz)
+}
+
 //go:noescape
-func msanread(addr unsafe.Pointer, sz uintptr)
+func domsanread(addr unsafe.Pointer, sz uintptr)
 
 //go:noescape
 func msanwrite(addr unsafe.Pointer, sz uintptr)
diff --git a/src/runtime/msan_amd64.s b/src/runtime/msan_amd64.s
index 6e8c1a10fc..613149593f 100644
--- a/src/runtime/msan_amd64.s
+++ b/src/runtime/msan_amd64.s
@@ -24,9 +24,9 @@
 #define RARG3 CX
 #endif
 
-// func runtime·msanread(addr unsafe.Pointer, sz uintptr)
-// Called from instrumented code.
-TEXT	runtime·msanread(SB), NOSPLIT, $0-16
+// func runtime·domsanread(addr unsafe.Pointer, sz uintptr)
+// Called from msanread.
+TEXT	runtime·domsanread(SB), NOSPLIT, $0-16
 	MOVQ	addr+0(FP), RARG0
 	MOVQ	size+8(FP), RARG1
 	// void __msan_read_go(void *addr, uintptr_t sz);