diff --git a/src/pkg/runtime/malloc.goc b/src/pkg/runtime/malloc.goc
index f8aa1c949e..a96372451c 100644
--- a/src/pkg/runtime/malloc.goc
+++ b/src/pkg/runtime/malloc.goc
@@ -434,6 +434,8 @@ runtime·MHeap_SysAlloc(MHeap *h, uintptr n)
 		runtime·SysMap(p, n);
 		h->arena_used += n;
 		runtime·MHeap_MapBits(h);
+		if(raceenabled)
+			runtime·racemapshadow(p, n);
 		return p;
 	}
 	
@@ -460,6 +462,8 @@ runtime·MHeap_SysAlloc(MHeap *h, uintptr n)
 		if(h->arena_used > h->arena_end)
 			h->arena_end = h->arena_used;
 		runtime·MHeap_MapBits(h);
+		if(raceenabled)
+			runtime·racemapshadow(p, n);
 	}
 	
 	return p;
diff --git a/src/pkg/runtime/race.c b/src/pkg/runtime/race.c
index ef7eec2b6b..49c7d4eb2c 100644
--- a/src/pkg/runtime/race.c
+++ b/src/pkg/runtime/race.c
@@ -11,6 +11,7 @@
 #include "race.h"
 
 void runtime∕race·Initialize(void);
+void runtime∕race·MapShadow(void *addr, uintptr size);
 void runtime∕race·Finalize(void);
 void runtime∕race·FinalizerGoroutine(int32);
 void runtime∕race·Read(int32 goid, void *addr, void *pc);
@@ -35,6 +36,7 @@ runtime·raceinit(void)
 {
 	m->racecall = true;
 	runtime∕race·Initialize();
+	runtime∕race·MapShadow(noptrdata, enoptrbss - noptrdata);
 	m->racecall = false;
 }
 
@@ -46,6 +48,14 @@ runtime·racefini(void)
 	m->racecall = false;
 }
 
+void
+runtime·racemapshadow(void *addr, uintptr size)
+{
+	m->racecall = true;
+	runtime∕race·MapShadow(addr, size);
+	m->racecall = false;
+}
+
 // Called from instrumented code.
 // If we split stack, getcallerpc() can return runtime·lessstack().
 #pragma textflag 7
diff --git a/src/pkg/runtime/race.h b/src/pkg/runtime/race.h
index eea1f9465e..9ebb9d3738 100644
--- a/src/pkg/runtime/race.h
+++ b/src/pkg/runtime/race.h
@@ -15,6 +15,7 @@ void	runtime·raceinit(void);
 // Finalize race detection subsystem, does not return.
 void	runtime·racefini(void);
 
+void	runtime·racemapshadow(void *addr, uintptr size);
 void	runtime·racemalloc(void *p, uintptr sz, void *pc);
 void	runtime·racefree(void *p);
 void	runtime·racegostart(int32 goid, void *pc);
diff --git a/src/pkg/runtime/race/race.go b/src/pkg/runtime/race/race.go
index f3a7be50c6..fb59ee8338 100644
--- a/src/pkg/runtime/race/race.go
+++ b/src/pkg/runtime/race/race.go
@@ -10,6 +10,7 @@ package race
 /*
 void __tsan_init(void);
 void __tsan_fini(void);
+void __tsan_map_shadow(void *addr, void *size);
 void __tsan_go_start(int pgoid, int chgoid, void *pc);
 void __tsan_go_end(int goid);
 void __tsan_read(int goid, void *addr, void *pc);
@@ -38,6 +39,10 @@ func Finalize() {
 	C.__tsan_fini()
 }
 
+func MapShadow(addr, size uintptr) {
+	C.__tsan_map_shadow(unsafe.Pointer(addr), unsafe.Pointer(size))
+}
+
 func FinalizerGoroutine(goid int32) {
 	C.__tsan_finalizer_goroutine(C.int(goid))
 }
diff --git a/src/pkg/runtime/race/race_darwin_amd64.syso b/src/pkg/runtime/race/race_darwin_amd64.syso
index b291e8e078..b323a71297 100644
Binary files a/src/pkg/runtime/race/race_darwin_amd64.syso and b/src/pkg/runtime/race/race_darwin_amd64.syso differ
diff --git a/src/pkg/runtime/race/race_linux_amd64.syso b/src/pkg/runtime/race/race_linux_amd64.syso
index c8e331f716..ccc42e57ca 100644
Binary files a/src/pkg/runtime/race/race_linux_amd64.syso and b/src/pkg/runtime/race/race_linux_amd64.syso differ
diff --git a/src/pkg/runtime/race0.c b/src/pkg/runtime/race0.c
index b650a14712..82ebba8229 100644
--- a/src/pkg/runtime/race0.c
+++ b/src/pkg/runtime/race0.c
@@ -17,6 +17,14 @@ runtime·racefini(void)
 {
 }
 
+
+void
+runtime·racemapshadow(void *addr, uintptr size)
+{
+	USED(addr);
+	USED(size);
+}
+
 void
 runtime·racewritepc(void *addr, void *pc)
 {