diff --git a/lib/time/update.bash b/lib/time/update.bash
index 3ffadc2a..86b1f21 100755
--- a/lib/time/update.bash
+++ b/lib/time/update.bash
@@ -8,8 +8,8 @@
 # Consult http://www.iana.org/time-zones for the latest versions.
 
 # Versions to use.
-CODE=2015g
-DATA=2015g
+CODE=2016a
+DATA=2016a
 
 set -e
 rm -rf work
diff --git a/lib/time/zoneinfo.zip b/lib/time/zoneinfo.zip
index 740d819..0207d6b 100644
--- a/lib/time/zoneinfo.zip
+++ b/lib/time/zoneinfo.zip
Binary files differ
diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 5db4bc6..c81bd40 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -93,7 +93,8 @@
 		Supported only on linux/amd64, freebsd/amd64, darwin/amd64 and windows/amd64.
 	-msan
 		enable interoperation with memory sanitizer.
-		Supported only on linux/amd64.
+		Supported only on linux/amd64,
+		and only with Clang/LLVM as the host C compiler.
 	-v
 		print the names of packages as they are compiled.
 	-work
diff --git a/src/cmd/go/build.go b/src/cmd/go/build.go
index 1286700..a1f925e 100644
--- a/src/cmd/go/build.go
+++ b/src/cmd/go/build.go
@@ -72,7 +72,8 @@
 		Supported only on linux/amd64, freebsd/amd64, darwin/amd64 and windows/amd64.
 	-msan
 		enable interoperation with memory sanitizer.
-		Supported only on linux/amd64.
+		Supported only on linux/amd64,
+		and only with Clang/LLVM as the host C compiler.
 	-v
 		print the names of packages as they are compiled.
 	-work
diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index 0136ba4..6d12f75 100644
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -657,6 +657,9 @@
 	tg.setenv("TESTGO_IS_GO_RELEASE", "0")
 	tg.run("build", "-v", "-a", "math")
 	tg.grepStderr("runtime", "testgo build -a math in dev branch DID NOT build runtime, but should have")
+
+	// Everything is out of date. Rebuild to leave things in a better state.
+	tg.run("install", "std")
 }
 
 func TestGoBuildDashAInReleaseBranch(t *testing.T) {
@@ -672,11 +675,80 @@
 	tg.grepStderr("runtime", "testgo build -a math in release branch DID NOT build runtime, but should have")
 
 	// Now runtime.a is updated (newer mtime), so everything would look stale if not for being a release.
-	//
 	tg.run("build", "-v", "net/http")
 	tg.grepStderrNot("strconv", "testgo build -v net/http in release branch with newer runtime.a DID build strconv but should not have")
 	tg.grepStderrNot("golang.org/x/net/http2/hpack", "testgo build -v net/http in release branch with newer runtime.a DID build .../golang.org/x/net/http2/hpack but should not have")
 	tg.grepStderrNot("net/http", "testgo build -v net/http in release branch with newer runtime.a DID build net/http but should not have")
+
+	// Everything is out of date. Rebuild to leave things in a better state.
+	tg.run("install", "std")
+}
+
+func TestNewReleaseRebuildsStalePackagesInGOPATH(t *testing.T) {
+	if testing.Short() {
+		t.Skip("don't rebuild the standard library in short mode")
+	}
+
+	tg := testgo(t)
+	defer tg.cleanup()
+
+	addNL := func(name string) (restore func()) {
+		data, err := ioutil.ReadFile(name)
+		if err != nil {
+			t.Fatal(err)
+		}
+		old := data
+		data = append(data, '\n')
+		if err := ioutil.WriteFile(name, append(data, '\n'), 0666); err != nil {
+			t.Fatal(err)
+		}
+		tg.sleep()
+		return func() {
+			if err := ioutil.WriteFile(name, old, 0666); err != nil {
+				t.Fatal(err)
+			}
+		}
+	}
+
+	tg.setenv("TESTGO_IS_GO_RELEASE", "1")
+
+	tg.tempFile("d1/src/p1/p1.go", `package p1`)
+	tg.setenv("GOPATH", tg.path("d1"))
+	tg.run("install", "-a", "p1")
+	tg.wantNotStale("p1", "./testgo list claims p1 is stale, incorrectly")
+	tg.sleep()
+
+	// Changing mtime and content of runtime/internal/sys/sys.go
+	// should have no effect: we're in a release, which doesn't rebuild
+	// for general mtime or content changes.
+	sys := runtime.GOROOT() + "/src/runtime/internal/sys/sys.go"
+	restore := addNL(sys)
+	defer restore()
+	tg.wantNotStale("p1", "./testgo list claims p1 is stale, incorrectly, after updating runtime/internal/sys/sys.go")
+	restore()
+	tg.wantNotStale("p1", "./testgo list claims p1 is stale, incorrectly, after restoring runtime/internal/sys/sys.go")
+
+	// But changing runtime/internal/sys/zversion.go should have an effect:
+	// that's how we tell when we flip from one release to another.
+	zversion := runtime.GOROOT() + "/src/runtime/internal/sys/zversion.go"
+	restore = addNL(zversion)
+	defer restore()
+	tg.wantStale("p1", "./testgo list claims p1 is NOT stale, incorrectly, after changing to new release")
+	restore()
+	tg.wantNotStale("p1", "./testgo list claims p1 is stale, incorrectly, after changing back to old release")
+	addNL(zversion)
+	tg.wantStale("p1", "./testgo list claims p1 is NOT stale, incorrectly, after changing again to new release")
+	tg.run("install", "p1")
+	tg.wantNotStale("p1", "./testgo list claims p1 is stale after building with new release")
+
+	// Restore to "old" release.
+	restore()
+	tg.wantStale("p1", "./testgo list claims p1 is NOT stale, incorrectly, after changing to old release after new build")
+	tg.run("install", "p1")
+	tg.wantNotStale("p1", "./testgo list claims p1 is stale after building with old release")
+
+	// Everything is out of date. Rebuild to leave things in a better state.
+	tg.run("install", "std")
 }
 
 func TestGoListStandard(t *testing.T) {
@@ -756,8 +828,8 @@
 	sep := string(filepath.ListSeparator)
 	tg.setenv("GOPATH", tg.path("d1")+sep+tg.path("d2"))
 	tg.run("install", "p1")
-	tg.wantNotStale("p1", "./testgo list mypkg claims p1 is stale, incorrectly")
-	tg.wantNotStale("p2", "./testgo list mypkg claims p2 is stale, incorrectly")
+	tg.wantNotStale("p1", "./testgo list claims p1 is stale, incorrectly")
+	tg.wantNotStale("p2", "./testgo list claims p2 is stale, incorrectly")
 	tg.sleep()
 	if f, err := os.OpenFile(tg.path("d2/src/p2/p2.go"), os.O_WRONLY|os.O_APPEND, 0); err != nil {
 		t.Fatal(err)
@@ -766,12 +838,12 @@
 	} else {
 		tg.must(f.Close())
 	}
-	tg.wantStale("p2", "./testgo list mypkg claims p2 is NOT stale, incorrectly")
-	tg.wantStale("p1", "./testgo list mypkg claims p1 is NOT stale, incorrectly")
+	tg.wantStale("p2", "./testgo list claims p2 is NOT stale, incorrectly")
+	tg.wantStale("p1", "./testgo list claims p1 is NOT stale, incorrectly")
 
 	tg.run("install", "p1")
-	tg.wantNotStale("p2", "./testgo list mypkg claims p2 is stale after reinstall, incorrectly")
-	tg.wantNotStale("p1", "./testgo list mypkg claims p1 is stale after reinstall, incorrectly")
+	tg.wantNotStale("p2", "./testgo list claims p2 is stale after reinstall, incorrectly")
+	tg.wantNotStale("p1", "./testgo list claims p1 is stale after reinstall, incorrectly")
 }
 
 func TestGoInstallDetectsRemovedFiles(t *testing.T) {
diff --git a/src/cmd/go/pkg.go b/src/cmd/go/pkg.go
index 95a06ff..a804ccd 100644
--- a/src/cmd/go/pkg.go
+++ b/src/cmd/go/pkg.go
@@ -1542,11 +1542,14 @@
 		fmt.Fprintf(h, "file %s\n", file)
 	}
 
-	// Include the content of runtime/zversion.go in the hash
+	// Include the content of runtime/internal/sys/zversion.go in the hash
 	// for package runtime. This will give package runtime a
 	// different build ID in each Go release.
-	if p.Standard && p.ImportPath == "runtime" {
-		data, _ := ioutil.ReadFile(filepath.Join(p.Dir, "zversion.go"))
+	if p.Standard && p.ImportPath == "runtime/internal/sys" {
+		data, err := ioutil.ReadFile(filepath.Join(p.Dir, "zversion.go"))
+		if err != nil {
+			fatalf("go: %s", err)
+		}
 		fmt.Fprintf(h, "zversion %q\n", string(data))
 	}
 
diff --git a/src/cmd/vet/cgo.go b/src/cmd/vet/cgo.go
index 8807952..1985a86 100644
--- a/src/cmd/vet/cgo.go
+++ b/src/cmd/vet/cgo.go
@@ -72,6 +72,9 @@
 		}
 		// Here arg is *f(v).
 		t := f.pkg.types[call.Fun].Type
+		if t == nil {
+			break
+		}
 		ptr, ok := t.Underlying().(*types.Pointer)
 		if !ok {
 			break
diff --git a/src/cmd/vet/testdata/cgo2.go b/src/cmd/vet/testdata/cgo2.go
new file mode 100644
index 0000000..276aea9
--- /dev/null
+++ b/src/cmd/vet/testdata/cgo2.go
@@ -0,0 +1,9 @@
+// Copyright 2016 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.
+
+// Test the cgo checker on a file that doesn't use cgo.
+
+package testdata
+
+var _ = C.f(*p(**p))
diff --git a/src/net/http/httputil/reverseproxy.go b/src/net/http/httputil/reverseproxy.go
index 4dba352..54411ca 100644
--- a/src/net/http/httputil/reverseproxy.go
+++ b/src/net/http/httputil/reverseproxy.go
@@ -106,11 +106,12 @@
 // http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html
 var hopHeaders = []string{
 	"Connection",
+	"Proxy-Connection", // non-standard but still sent by libcurl and rejected by e.g. google
 	"Keep-Alive",
 	"Proxy-Authenticate",
 	"Proxy-Authorization",
-	"Te", // canonicalized version of "TE"
-	"Trailers",
+	"Te",      // canonicalized version of "TE"
+	"Trailer", // not Trailers per URL above; http://www.rfc-editor.org/errata_search.php?eid=4522
 	"Transfer-Encoding",
 	"Upgrade",
 }
diff --git a/src/net/http/httputil/reverseproxy_test.go b/src/net/http/httputil/reverseproxy_test.go
index 7f203d8..0849427 100644
--- a/src/net/http/httputil/reverseproxy_test.go
+++ b/src/net/http/httputil/reverseproxy_test.go
@@ -45,9 +45,13 @@
 		if c := r.Header.Get("Upgrade"); c != "" {
 			t.Errorf("handler got Upgrade header value %q", c)
 		}
+		if c := r.Header.Get("Proxy-Connection"); c != "" {
+			t.Errorf("handler got Proxy-Connection header value %q", c)
+		}
 		if g, e := r.Host, "some-name"; g != e {
 			t.Errorf("backend got Host header %q, want %q", g, e)
 		}
+		w.Header().Set("Trailers", "not a special header field name")
 		w.Header().Set("Trailer", "X-Trailer")
 		w.Header().Set("X-Foo", "bar")
 		w.Header().Set("Upgrade", "foo")
@@ -71,6 +75,7 @@
 	getReq, _ := http.NewRequest("GET", frontend.URL, nil)
 	getReq.Host = "some-name"
 	getReq.Header.Set("Connection", "close")
+	getReq.Header.Set("Proxy-Connection", "should be deleted")
 	getReq.Header.Set("Upgrade", "foo")
 	getReq.Close = true
 	res, err := http.DefaultClient.Do(getReq)
@@ -86,6 +91,9 @@
 	if c := res.Header.Get(fakeHopHeader); c != "" {
 		t.Errorf("got %s header value %q", fakeHopHeader, c)
 	}
+	if g, e := res.Header.Get("Trailers"), "not a special header field name"; g != e {
+		t.Errorf("header Trailers = %q; want %q", g, e)
+	}
 	if g, e := len(res.Header["X-Multi-Value"]), 2; g != e {
 		t.Errorf("got %d X-Multi-Value header values; expected %d", g, e)
 	}
diff --git a/src/net/http/transport_test.go b/src/net/http/transport_test.go
index 3b2a5f9..8cb89a4 100644
--- a/src/net/http/transport_test.go
+++ b/src/net/http/transport_test.go
@@ -2208,9 +2208,8 @@
 // Trying to repro golang.org/issue/3514
 func TestTLSServerClosesConnection(t *testing.T) {
 	defer afterTest(t)
-	if runtime.GOOS == "windows" {
-		t.Skip("skipping flaky test on Windows; golang.org/issue/7634")
-	}
+	setFlaky(t, 7634)
+
 	closedc := make(chan bool, 1)
 	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		if strings.Contains(r.URL.Path, "/keep-alive-then-die") {
diff --git a/src/runtime/pprof/pprof_test.go b/src/runtime/pprof/pprof_test.go
index 621d21d..ab6b183 100644
--- a/src/runtime/pprof/pprof_test.go
+++ b/src/runtime/pprof/pprof_test.go
@@ -96,7 +96,7 @@
 	if l < 5+3 {
 		t.Logf("profile too short: %#x", val)
 		if badOS[runtime.GOOS] {
-			t.Skipf("ignoring failure on %s; see golang.org/issue/6047", runtime.GOOS)
+			t.Skipf("ignoring failure on %s; see golang.org/issue/13841", runtime.GOOS)
 			return
 		}
 		t.FailNow()
@@ -171,7 +171,7 @@
 	}
 
 	if badOS[runtime.GOOS] {
-		t.Skipf("ignoring failure on %s; see golang.org/issue/6047", runtime.GOOS)
+		t.Skipf("ignoring failure on %s; see golang.org/issue/13841", runtime.GOOS)
 		return
 	}
 	// Ignore the failure if the tests are running in a QEMU-based emulator,
@@ -420,11 +420,13 @@
 	return deepStack(depth-1) + 1
 }
 
-// Operating systems that are expected to fail the tests. See issue 6047.
+// Operating systems that are expected to fail the tests. See issue 13841.
 var badOS = map[string]bool{
-	"darwin": true,
-	"netbsd": true,
-	"plan9":  true,
+	"darwin":    true,
+	"netbsd":    true,
+	"plan9":     true,
+	"dragonfly": true,
+	"solaris":   true,
 }
 
 func TestBlockProfile(t *testing.T) {
diff --git a/src/sync/waitgroup_test.go b/src/sync/waitgroup_test.go
index a5816609..8ec34fd 100644
--- a/src/sync/waitgroup_test.go
+++ b/src/sync/waitgroup_test.go
@@ -128,13 +128,16 @@
 		}
 	}()
 	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(4))
-	done := make(chan interface{}, 1)
+	done := make(chan interface{}, 2)
 	// The detection is opportunistically, so we want it to panic
 	// at least in one run out of a million.
 	for i := 0; i < 1e6; i++ {
 		var wg WaitGroup
 		wg.Add(1)
 		go func() {
+			defer func() {
+				done <- recover()
+			}()
 			wg.Done()
 		}()
 		go func() {
@@ -150,8 +153,10 @@
 			wg.Wait()
 		}()
 		wg.Wait()
-		if err := <-done; err != nil {
-			panic(err)
+		for j := 0; j < 2; j++ {
+			if err := <-done; err != nil {
+				panic(err)
+			}
 		}
 	}
 	t.Fatal("Should panic")