diff --git a/src/crypto/x509/root_cgo_darwin.go b/src/crypto/x509/root_cgo_darwin.go
index 5c310bff09..11515b82d0 100644
--- a/src/crypto/x509/root_cgo_darwin.go
+++ b/src/crypto/x509/root_cgo_darwin.go
@@ -16,59 +16,6 @@ package x509
 #include <CoreFoundation/CoreFoundation.h>
 #include <Security/Security.h>
 
-// FetchPEMRoots_MountainLion is the version of FetchPEMRoots from Go 1.6
-// which still works on OS X 10.8 (Mountain Lion).
-// It lacks support for admin & user cert domains.
-// See golang.org/issue/16473
-int FetchPEMRoots_MountainLion(CFDataRef *pemRoots) {
-	if (pemRoots == NULL) {
-		return -1;
-	}
-	CFArrayRef certs = NULL;
-	OSStatus err = SecTrustCopyAnchorCertificates(&certs);
-	if (err != noErr) {
-		return -1;
-	}
-	CFMutableDataRef combinedData = CFDataCreateMutable(kCFAllocatorDefault, 0);
-	int i, ncerts = CFArrayGetCount(certs);
-	for (i = 0; i < ncerts; i++) {
-		CFDataRef data = NULL;
-		SecCertificateRef cert = (SecCertificateRef)CFArrayGetValueAtIndex(certs, i);
-		if (cert == NULL) {
-			continue;
-		}
-		// Note: SecKeychainItemExport is deprecated as of 10.7 in favor of SecItemExport.
-		// Once we support weak imports via cgo we should prefer that, and fall back to this
-		// for older systems.
-		err = SecKeychainItemExport(cert, kSecFormatX509Cert, kSecItemPemArmour, NULL, &data);
-		if (err != noErr) {
-			continue;
-		}
-		if (data != NULL) {
-			CFDataAppendBytes(combinedData, CFDataGetBytePtr(data), CFDataGetLength(data));
-			CFRelease(data);
-		}
-	}
-	CFRelease(certs);
-	*pemRoots = combinedData;
-	return 0;
-}
-
-// useOldCode reports whether the running machine is OS X 10.8 Mountain Lion
-// or older. We only support Mountain Lion and higher, but we'll at least try our
-// best on older machines and continue to use the old code path.
-//
-// See golang.org/issue/16473
-int useOldCode() {
-	char str[256];
-	size_t size = sizeof(str);
-	memset(str, 0, size);
-	sysctlbyname("kern.osrelease", str, &size, NULL, 0);
-	// OS X 10.8 is osrelease "12.*", 10.7 is 11.*, 10.6 is 10.*.
-	// We never supported things before that.
-	return memcmp(str, "12.", 3) == 0 || memcmp(str, "11.", 3) == 0 || memcmp(str, "10.", 3) == 0;
-}
-
 // FetchPEMRoots fetches the system's list of trusted X.509 root certificates.
 //
 // On success it returns 0 and fills pemRoots with a CFDataRef that contains the extracted root
@@ -80,10 +27,6 @@ int useOldCode() {
 int FetchPEMRoots(CFDataRef *pemRoots, CFDataRef *untrustedPemRoots) {
 	int i;
 
-	if (useOldCode()) {
-		return FetchPEMRoots_MountainLion(pemRoots);
-	}
-
 	// Get certificates from all domains, not just System, this lets
 	// the user add CAs to their "login" keychain, and Admins to add
 	// to the "System" keychain
diff --git a/src/net/fd_unix.go b/src/net/fd_unix.go
index 145933e737..3dcbeb51c7 100644
--- a/src/net/fd_unix.go
+++ b/src/net/fd_unix.go
@@ -263,19 +263,6 @@ var tryDupCloexec = int32(1)
 func dupCloseOnExec(fd int) (newfd int, err error) {
 	if atomic.LoadInt32(&tryDupCloexec) == 1 {
 		r0, _, e1 := syscall.Syscall(syscall.SYS_FCNTL, uintptr(fd), syscall.F_DUPFD_CLOEXEC, 0)
-		if runtime.GOOS == "darwin" && e1 == syscall.EBADF {
-			// On OS X 10.6 and below (but we only support
-			// >= 10.6), F_DUPFD_CLOEXEC is unsupported
-			// and fcntl there falls back (undocumented)
-			// to doing an ioctl instead, returning EBADF
-			// in this case because fd is not of the
-			// expected device fd type. Treat it as
-			// EINVAL instead, so we fall back to the
-			// normal dup path.
-			// TODO: only do this on 10.6 if we can detect 10.6
-			// cheaply.
-			e1 = syscall.EINVAL
-		}
 		switch e1 {
 		case 0:
 			return int(r0), nil
diff --git a/src/runtime/crash_cgo_test.go b/src/runtime/crash_cgo_test.go
index fc0cfd9aed..d8f75a468b 100644
--- a/src/runtime/crash_cgo_test.go
+++ b/src/runtime/crash_cgo_test.go
@@ -89,19 +89,6 @@ func TestCgoExternalThreadSIGPROF(t *testing.T) {
 	switch runtime.GOOS {
 	case "plan9", "windows":
 		t.Skipf("no pthreads on %s", runtime.GOOS)
-	case "darwin":
-		if runtime.GOARCH != "arm" && runtime.GOARCH != "arm64" {
-			// static constructor needs external linking, but we don't support
-			// external linking on OS X 10.6.
-			out, err := exec.Command("uname", "-r").Output()
-			if err != nil {
-				t.Fatalf("uname -r failed: %v", err)
-			}
-			// OS X 10.6 == Darwin 10.x
-			if strings.HasPrefix(string(out), "10.") {
-				t.Skipf("no external linking on OS X 10.6")
-			}
-		}
 	}
 	if runtime.GOARCH == "ppc64" {
 		// TODO(austin) External linking not implemented on