diff --git a/src/cmd/gc/builtin.c b/src/cmd/gc/builtin.c
index 9053dfe108..baa7d7845a 100644
--- a/src/cmd/gc/builtin.c
+++ b/src/cmd/gc/builtin.c
@@ -113,6 +113,8 @@ char *runtimeimport =
 	"func @\"\".racefuncexit ()\n"
 	"func @\"\".raceread (? uintptr)\n"
 	"func @\"\".racewrite (? uintptr)\n"
+	"func @\"\".racereadrange (@\"\".addr·1 uintptr, @\"\".size·2 uintptr)\n"
+	"func @\"\".racewriterange (@\"\".addr·1 uintptr, @\"\".size·2 uintptr)\n"
 	"\n"
 	"$$\n";
 char *unsafeimport =
diff --git a/src/cmd/gc/racewalk.c b/src/cmd/gc/racewalk.c
index 74d8522580..0c847d8bb8 100644
--- a/src/cmd/gc/racewalk.c
+++ b/src/cmd/gc/racewalk.c
@@ -439,8 +439,8 @@ static int
 callinstr(Node **np, NodeList **init, int wr, int skip)
 {
 	Node *f, *b, *n;
-	Type *t, *t1;
-	int class, res, hascalls;
+	Type *t;
+	int class, hascalls;
 
 	n = *np;
 	//print("callinstr for %+N [ %O ] etype=%E class=%d\n",
@@ -451,33 +451,6 @@ callinstr(Node **np, NodeList **init, int wr, int skip)
 	t = n->type;
 	if(isartificial(n))
 		return 0;
-	if(t->etype == TSTRUCT) {
-		// TODO: instrument arrays similarly.
-		// PARAMs w/o PHEAP are not interesting.
-		if(n->class == PPARAM || n->class == PPARAMOUT)
-			return 0;
-		res = 0;
-		hascalls = 0;
-		foreach(n, hascallspred, &hascalls);
-		if(hascalls) {
-			n = detachexpr(n, init);
-			*np = n;
-		}
-		for(t1=t->type; t1; t1=t1->down) {
-			if(t1->sym && strcmp(t1->sym->name, "_")) {
-				n = treecopy(n);
-				f = nod(OXDOT, n, newname(t1->sym));
-				f->type = t1;
-				if(f->type->etype == TFIELD)
-					f->type = f->type->type;
-				if(callinstr(&f, init, wr, 0)) {
-					typecheck(&f, Erv);
-					res = 1;
-				}
-			}
-		}
-		return res;
-	}
 
 	b = basenod(n);
 	// it skips e.g. stores to ... parameter array
@@ -498,7 +471,11 @@ callinstr(Node **np, NodeList **init, int wr, int skip)
 		}
 		n = treecopy(n);
 		makeaddable(n);
-		f = mkcall(wr ? "racewrite" : "raceread", T, init, uintptraddr(n));
+		if(t->etype == TSTRUCT || isfixedarray(t)) {
+			f = mkcall(wr ? "racewriterange" : "racereadrange", T, init, uintptraddr(n),
+					nodintconst(t->width));
+		} else
+			f = mkcall(wr ? "racewrite" : "raceread", T, init, uintptraddr(n));
 		*init = list(*init, f);
 		return 1;
 	}
diff --git a/src/cmd/gc/runtime.go b/src/cmd/gc/runtime.go
index 2139a95d93..d7032957b1 100644
--- a/src/cmd/gc/runtime.go
+++ b/src/cmd/gc/runtime.go
@@ -149,3 +149,5 @@ func racefuncenter(uintptr)
 func racefuncexit()
 func raceread(uintptr)
 func racewrite(uintptr)
+func racereadrange(addr, size uintptr)
+func racewriterange(addr, size uintptr)
diff --git a/src/pkg/runtime/race.c b/src/pkg/runtime/race.c
index 765a4b5502..557da6f8e3 100644
--- a/src/pkg/runtime/race.c
+++ b/src/pkg/runtime/race.c
@@ -77,6 +77,17 @@ runtime·racewrite(uintptr addr)
 	}
 }
 
+#pragma textflag 7
+void
+runtime·racewriterange(uintptr addr, uintptr sz)
+{
+	if(!onstack(addr)) {
+		m->racecall = true;
+		runtime∕race·WriteRange(g->racectx, (void*)addr, sz, runtime·getcallerpc(&addr));
+		m->racecall = false;
+	}
+}
+
 // Called from instrumented code.
 // If we split stack, getcallerpc() can return runtime·lessstack().
 #pragma textflag 7
@@ -90,6 +101,17 @@ runtime·raceread(uintptr addr)
 	}
 }
 
+#pragma textflag 7
+void
+runtime·racereadrange(uintptr addr, uintptr sz)
+{
+	if(!onstack(addr)) {
+		m->racecall = true;
+		runtime∕race·ReadRange(g->racectx, (void*)addr, sz, runtime·getcallerpc(&addr));
+		m->racecall = false;
+	}
+}
+
 // Called from runtime·racefuncenter (assembly).
 #pragma textflag 7
 void
diff --git a/src/pkg/runtime/race/testdata/mop_test.go b/src/pkg/runtime/race/testdata/mop_test.go
index 620b7ab6e4..9a0cb81f53 100644
--- a/src/pkg/runtime/race/testdata/mop_test.go
+++ b/src/pkg/runtime/race/testdata/mop_test.go
@@ -600,8 +600,7 @@ func TestRaceSprint(t *testing.T) {
 	<-ch
 }
 
-// Not implemented.
-func TestRaceFailingArrayCopy(t *testing.T) {
+func TestRaceArrayCopy(t *testing.T) {
 	ch := make(chan bool, 1)
 	var a [5]int
 	go func() {
@@ -612,6 +611,24 @@ func TestRaceFailingArrayCopy(t *testing.T) {
 	<-ch
 }
 
+// Blows up a naive compiler.
+func TestRaceNestedArrayCopy(t *testing.T) {
+	ch := make(chan bool, 1)
+	type (
+		Point32   [2][2][2][2][2]Point
+		Point1024 [2][2][2][2][2]Point32
+		Point32k  [2][2][2][2][2]Point1024
+		Point1M   [2][2][2][2][2]Point32k
+	)
+	var a, b Point1M
+	go func() {
+		a[0][1][0][1][0][1][0][1][0][1][0][1][0][1][0][1][0][1][0][1].y = 1
+		ch <- true
+	}()
+	a = b
+	<-ch
+}
+
 func TestRaceStructRW(t *testing.T) {
 	p := Point{0, 0}
 	ch := make(chan bool, 1)