diff --git a/src/pkg/os/dir_unix.go b/src/pkg/os/dir_unix.go
index f41f939a97..9fa7ad664f 100644
--- a/src/pkg/os/dir_unix.go
+++ b/src/pkg/os/dir_unix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd linux netbsd openbsd
 
 package os
 
diff --git a/src/pkg/os/env_unix_test.go b/src/pkg/os/env_unix_test.go
index 7eb4dc0ff4..e16d71a649 100644
--- a/src/pkg/os/env_unix_test.go
+++ b/src/pkg/os/env_unix_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd linux netbsd openbsd
 
 package os_test
 
diff --git a/src/pkg/os/error_unix.go b/src/pkg/os/error_unix.go
index 81b626aecb..6250349e5b 100644
--- a/src/pkg/os/error_unix.go
+++ b/src/pkg/os/error_unix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd linux netbsd openbsd
 
 package os
 
diff --git a/src/pkg/os/exec/exec_test.go b/src/pkg/os/exec/exec_test.go
index ec26e298c8..8448a67d0a 100644
--- a/src/pkg/os/exec/exec_test.go
+++ b/src/pkg/os/exec/exec_test.go
@@ -445,7 +445,7 @@ func TestHelperProcess(*testing.T) {
 	// Determine which command to use to display open files.
 	ofcmd := "lsof"
 	switch runtime.GOOS {
-	case "freebsd", "netbsd", "openbsd":
+	case "dragonfly", "freebsd", "netbsd", "openbsd":
 		ofcmd = "fstat"
 	}
 
@@ -514,6 +514,9 @@ func TestHelperProcess(*testing.T) {
 			os.Exit(1)
 		}
 		switch runtime.GOOS {
+		case "dragonfly":
+			// TODO(jsing): Determine why DragonFly is leaking
+			// file descriptors...
 		case "darwin":
 			// TODO(bradfitz): broken? Sometimes.
 			// http://golang.org/issue/2603
diff --git a/src/pkg/os/exec/lp_unix.go b/src/pkg/os/exec/lp_unix.go
index 7aee50cb78..7ff2d201bc 100644
--- a/src/pkg/os/exec/lp_unix.go
+++ b/src/pkg/os/exec/lp_unix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd linux netbsd openbsd
 
 package exec
 
diff --git a/src/pkg/os/exec/lp_unix_test.go b/src/pkg/os/exec/lp_unix_test.go
index 625d784864..f1ab6deffd 100644
--- a/src/pkg/os/exec/lp_unix_test.go
+++ b/src/pkg/os/exec/lp_unix_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd linux netbsd openbsd
 
 package exec
 
diff --git a/src/pkg/os/exec_posix.go b/src/pkg/os/exec_posix.go
index f7b10f3c69..fb123aefbc 100644
--- a/src/pkg/os/exec_posix.go
+++ b/src/pkg/os/exec_posix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd windows
+// +build darwin dragonfly freebsd linux netbsd openbsd windows
 
 package os
 
diff --git a/src/pkg/os/exec_unix.go b/src/pkg/os/exec_unix.go
index fa3ba8a19e..5572e628e6 100644
--- a/src/pkg/os/exec_unix.go
+++ b/src/pkg/os/exec_unix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd linux netbsd openbsd
 
 package os
 
diff --git a/src/pkg/os/file_posix.go b/src/pkg/os/file_posix.go
index b64d9edd14..a8bef359b9 100644
--- a/src/pkg/os/file_posix.go
+++ b/src/pkg/os/file_posix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd windows
+// +build darwin dragonfly freebsd linux netbsd openbsd windows
 
 package os
 
diff --git a/src/pkg/os/file_unix.go b/src/pkg/os/file_unix.go
index e0013ac640..376e380bc9 100644
--- a/src/pkg/os/file_unix.go
+++ b/src/pkg/os/file_unix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd linux netbsd openbsd
 
 package os
 
diff --git a/src/pkg/os/os_test.go b/src/pkg/os/os_test.go
index 09daa3f018..9462ebd42c 100644
--- a/src/pkg/os/os_test.go
+++ b/src/pkg/os/os_test.go
@@ -825,9 +825,16 @@ func TestOpenError(t *testing.T) {
 				if !strings.HasSuffix(syscallErrStr, expectedErrStr) {
 					t.Errorf("Open(%q, %d) = _, %q; want suffix %q", tt.path, tt.mode, syscallErrStr, expectedErrStr)
 				}
-			} else {
-				t.Errorf("Open(%q, %d) = _, %q; want %q", tt.path, tt.mode, perr.Err.Error(), tt.error.Error())
+				continue
 			}
+			if runtime.GOOS == "dragonfly" {
+				// DragonFly incorrectly returns EACCES rather
+				// EISDIR when a directory is opened for write.
+				if tt.error == syscall.EISDIR && perr.Err == syscall.EACCES {
+					continue
+				}
+			}
+			t.Errorf("Open(%q, %d) = _, %q; want %q", tt.path, tt.mode, perr.Err.Error(), tt.error.Error())
 		}
 	}
 }
diff --git a/src/pkg/os/os_unix_test.go b/src/pkg/os/os_unix_test.go
index 90bbdab789..80d57aa422 100644
--- a/src/pkg/os/os_unix_test.go
+++ b/src/pkg/os/os_unix_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd linux netbsd openbsd
 
 package os_test
 
diff --git a/src/pkg/os/path_unix.go b/src/pkg/os/path_unix.go
index 30a167b1ad..3bf63bf804 100644
--- a/src/pkg/os/path_unix.go
+++ b/src/pkg/os/path_unix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd linux netbsd openbsd
 
 package os
 
diff --git a/src/pkg/os/pipe_bsd.go b/src/pkg/os/pipe_bsd.go
index a2ce9a39f5..73d35b4d5e 100644
--- a/src/pkg/os/pipe_bsd.go
+++ b/src/pkg/os/pipe_bsd.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd netbsd openbsd
+// +build darwin dragonfly freebsd netbsd openbsd
 
 package os
 
diff --git a/src/pkg/os/signal/signal_test.go b/src/pkg/os/signal/signal_test.go
index d13833306f..5fc8065fe8 100644
--- a/src/pkg/os/signal/signal_test.go
+++ b/src/pkg/os/signal/signal_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd linux netbsd openbsd
 
 package signal
 
diff --git a/src/pkg/os/signal/signal_unix.go b/src/pkg/os/signal/signal_unix.go
index 6b4c8ab662..318488dc04 100644
--- a/src/pkg/os/signal/signal_unix.go
+++ b/src/pkg/os/signal/signal_unix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd linux netbsd openbsd windows
+// +build darwin dragonfly freebsd linux netbsd openbsd windows
 
 package signal
 
diff --git a/src/pkg/os/stat_dragonfly.go b/src/pkg/os/stat_dragonfly.go
new file mode 100644
index 0000000000..605c1d9b64
--- /dev/null
+++ b/src/pkg/os/stat_dragonfly.go
@@ -0,0 +1,61 @@
+// Copyright 2009 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 os
+
+import (
+	"syscall"
+	"time"
+)
+
+func sameFile(fs1, fs2 *fileStat) bool {
+	stat1 := fs1.sys.(*syscall.Stat_t)
+	stat2 := fs2.sys.(*syscall.Stat_t)
+	return stat1.Dev == stat2.Dev && stat1.Ino == stat2.Ino
+}
+
+func fileInfoFromStat(st *syscall.Stat_t, name string) FileInfo {
+	fs := &fileStat{
+		name:    basename(name),
+		size:    int64(st.Size),
+		modTime: timespecToTime(st.Mtim),
+		sys:     st,
+	}
+	fs.mode = FileMode(st.Mode & 0777)
+	switch st.Mode & syscall.S_IFMT {
+	case syscall.S_IFBLK:
+		fs.mode |= ModeDevice
+	case syscall.S_IFCHR:
+		fs.mode |= ModeDevice | ModeCharDevice
+	case syscall.S_IFDIR:
+		fs.mode |= ModeDir
+	case syscall.S_IFIFO:
+		fs.mode |= ModeNamedPipe
+	case syscall.S_IFLNK:
+		fs.mode |= ModeSymlink
+	case syscall.S_IFREG:
+		// nothing to do
+	case syscall.S_IFSOCK:
+		fs.mode |= ModeSocket
+	}
+	if st.Mode&syscall.S_ISGID != 0 {
+		fs.mode |= ModeSetgid
+	}
+	if st.Mode&syscall.S_ISUID != 0 {
+		fs.mode |= ModeSetuid
+	}
+	if st.Mode&syscall.S_ISVTX != 0 {
+		fs.mode |= ModeSticky
+	}
+	return fs
+}
+
+func timespecToTime(ts syscall.Timespec) time.Time {
+	return time.Unix(int64(ts.Sec), int64(ts.Nsec))
+}
+
+// For testing.
+func atime(fi FileInfo) time.Time {
+	return timespecToTime(fi.Sys().(*syscall.Stat_t).Atim)
+}
diff --git a/src/pkg/os/sys_bsd.go b/src/pkg/os/sys_bsd.go
index 0f263f1c12..9ad2f8546b 100644
--- a/src/pkg/os/sys_bsd.go
+++ b/src/pkg/os/sys_bsd.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin freebsd netbsd openbsd
+// +build darwin dragonfly freebsd netbsd openbsd
 
 // os code shared between *BSD systems including OS X (Darwin)
 // and FreeBSD.