diff --git a/src/pkg/archive/tar/common.go b/src/pkg/archive/tar/common.go
index 4d399e5fe9d..5b781ff3d7d 100644
--- a/src/pkg/archive/tar/common.go
+++ b/src/pkg/archive/tar/common.go
@@ -33,8 +33,8 @@ const (
 type Header struct {
 	Name     string
 	Mode     int64
-	Uid      int64
-	Gid      int64
+	Uid      int
+	Gid      int
 	Size     int64
 	Mtime    int64
 	Typeflag byte
diff --git a/src/pkg/archive/tar/reader.go b/src/pkg/archive/tar/reader.go
index 7de559d337f..35a15f74bb1 100644
--- a/src/pkg/archive/tar/reader.go
+++ b/src/pkg/archive/tar/reader.go
@@ -142,8 +142,8 @@ func (tr *Reader) readHeader() *Header {
 
 	hdr.Name = cString(s.next(100))
 	hdr.Mode = tr.octal(s.next(8))
-	hdr.Uid = tr.octal(s.next(8))
-	hdr.Gid = tr.octal(s.next(8))
+	hdr.Uid = int(tr.octal(s.next(8)))
+	hdr.Gid = int(tr.octal(s.next(8)))
 	hdr.Size = tr.octal(s.next(12))
 	hdr.Mtime = tr.octal(s.next(12))
 	s.next(8) // chksum
diff --git a/src/pkg/archive/tar/writer.go b/src/pkg/archive/tar/writer.go
index 7f200c440b3..1f2656d3249 100644
--- a/src/pkg/archive/tar/writer.go
+++ b/src/pkg/archive/tar/writer.go
@@ -130,8 +130,8 @@ func (tw *Writer) WriteHeader(hdr *Header) os.Error {
 	copy(s.next(100), []byte(hdr.Name))
 
 	tw.octal(s.next(8), hdr.Mode)          // 100:108
-	tw.numeric(s.next(8), hdr.Uid)         // 108:116
-	tw.numeric(s.next(8), hdr.Gid)         // 116:124
+	tw.numeric(s.next(8), int64(hdr.Uid))  // 108:116
+	tw.numeric(s.next(8), int64(hdr.Gid))  // 116:124
 	tw.numeric(s.next(12), hdr.Size)       // 124:136
 	tw.numeric(s.next(12), hdr.Mtime)      // 136:148
 	s.next(8)                              // chksum (148:156)
diff --git a/src/pkg/io/ioutil/ioutil.go b/src/pkg/io/ioutil/ioutil.go
index 0f5a3a20ef5..d338693807f 100644
--- a/src/pkg/io/ioutil/ioutil.go
+++ b/src/pkg/io/ioutil/ioutil.go
@@ -30,7 +30,7 @@ func ReadFile(filename string) ([]byte, os.Error) {
 	// It's a good but not certain bet that FileInfo will tell us exactly how much to
 	// read, so let's try it but be prepared for the answer to be wrong.
 	fi, err := f.Stat()
-	var n uint64
+	var n int64
 	if err == nil && fi.Size < 2e9 { // Don't preallocate a huge buffer, just in case.
 		n = fi.Size
 	}
diff --git a/src/pkg/io/ioutil/ioutil_test.go b/src/pkg/io/ioutil/ioutil_test.go
index cc6075f9e6d..ecbf41ca669 100644
--- a/src/pkg/io/ioutil/ioutil_test.go
+++ b/src/pkg/io/ioutil/ioutil_test.go
@@ -10,7 +10,7 @@ import (
 	"testing"
 )
 
-func checkSize(t *testing.T, path string, size uint64) {
+func checkSize(t *testing.T, path string, size int64) {
 	dir, err := os.Stat(path)
 	if err != nil {
 		t.Fatalf("Stat %q (looking for size %d): %s", path, size, err)
@@ -33,7 +33,7 @@ func TestReadFile(t *testing.T) {
 		t.Fatalf("ReadFile %s: %v", filename, err)
 	}
 
-	checkSize(t, filename, uint64(len(contents)))
+	checkSize(t, filename, int64(len(contents)))
 }
 
 func TestWriteFile(t *testing.T) {
diff --git a/src/pkg/os/os_test.go b/src/pkg/os/os_test.go
index d8208bfe416..f4ccb524c14 100644
--- a/src/pkg/os/os_test.go
+++ b/src/pkg/os/os_test.go
@@ -33,7 +33,7 @@ var etc = []string{
 	"passwd",
 }
 
-func size(name string, t *testing.T) uint64 {
+func size(name string, t *testing.T) int64 {
 	file, err := Open(name, O_RDONLY, 0)
 	defer file.Close()
 	if err != nil {
@@ -51,7 +51,7 @@ func size(name string, t *testing.T) uint64 {
 			t.Fatal("read failed:", err)
 		}
 	}
-	return uint64(len)
+	return int64(len)
 }
 
 func TestStat(t *testing.T) {
@@ -394,10 +394,10 @@ func checkUidGid(t *testing.T, path string, uid, gid int) {
 	if err != nil {
 		t.Fatalf("Stat %q (looking for uid/gid %d/%d): %s", path, uid, gid, err)
 	}
-	if dir.Uid != uint32(uid) {
+	if dir.Uid != uid {
 		t.Errorf("Stat %q: uid %d want %d", path, dir.Uid, uid)
 	}
-	if dir.Gid != uint32(gid) {
+	if dir.Gid != gid {
 		t.Errorf("Stat %q: gid %d want %d", path, dir.Gid, gid)
 	}
 }
@@ -427,7 +427,7 @@ func TestChown(t *testing.T) {
 	if err = Chown(Path, -1, gid); err != nil {
 		t.Fatalf("chown %s -1 %d: %s", Path, gid, err)
 	}
-	checkUidGid(t, Path, int(dir.Uid), gid)
+	checkUidGid(t, Path, dir.Uid, gid)
 
 	// Then try all the auxiliary groups.
 	groups, err := Getgroups()
@@ -439,17 +439,17 @@ func TestChown(t *testing.T) {
 		if err = Chown(Path, -1, g); err != nil {
 			t.Fatalf("chown %s -1 %d: %s", Path, g, err)
 		}
-		checkUidGid(t, Path, int(dir.Uid), g)
+		checkUidGid(t, Path, dir.Uid, g)
 
 		// change back to gid to test fd.Chown
 		if err = fd.Chown(-1, gid); err != nil {
 			t.Fatalf("fchown %s -1 %d: %s", Path, gid, err)
 		}
-		checkUidGid(t, Path, int(dir.Uid), gid)
+		checkUidGid(t, Path, dir.Uid, gid)
 	}
 }
 
-func checkSize(t *testing.T, path string, size uint64) {
+func checkSize(t *testing.T, path string, size int64) {
 	dir, err := Stat(path)
 	if err != nil {
 		t.Fatalf("Stat %q (looking for size %d): %s", path, size, err)
diff --git a/src/pkg/os/stat_darwin.go b/src/pkg/os/stat_darwin.go
index 5ab2c39dfc0..8f4e6bafae3 100644
--- a/src/pkg/os/stat_darwin.go
+++ b/src/pkg/os/stat_darwin.go
@@ -15,15 +15,15 @@ func fileInfoFromStat(name string, fi *FileInfo, lstat, stat *syscall.Stat_t) *F
 	fi.Ino = stat.Ino
 	fi.Nlink = uint64(stat.Nlink)
 	fi.Mode = uint32(stat.Mode)
-	fi.Uid = stat.Uid
-	fi.Gid = stat.Gid
+	fi.Uid = int(stat.Uid)
+	fi.Gid = int(stat.Gid)
 	fi.Rdev = uint64(stat.Rdev)
-	fi.Size = uint64(stat.Size)
-	fi.Blksize = uint64(stat.Blksize)
-	fi.Blocks = uint64(stat.Blocks)
-	fi.Atime_ns = uint64(syscall.TimespecToNsec(stat.Atimespec))
-	fi.Mtime_ns = uint64(syscall.TimespecToNsec(stat.Mtimespec))
-	fi.Ctime_ns = uint64(syscall.TimespecToNsec(stat.Ctimespec))
+	fi.Size = stat.Size
+	fi.Blksize = int64(stat.Blksize)
+	fi.Blocks = stat.Blocks
+	fi.Atime_ns = syscall.TimespecToNsec(stat.Atimespec)
+	fi.Mtime_ns = syscall.TimespecToNsec(stat.Mtimespec)
+	fi.Ctime_ns = syscall.TimespecToNsec(stat.Ctimespec)
 	for i := len(name) - 1; i >= 0; i-- {
 		if name[i] == '/' {
 			name = name[i+1:]
diff --git a/src/pkg/os/stat_freebsd.go b/src/pkg/os/stat_freebsd.go
index dd33d8cc6e1..0646b29c560 100644
--- a/src/pkg/os/stat_freebsd.go
+++ b/src/pkg/os/stat_freebsd.go
@@ -15,15 +15,15 @@ func fileInfoFromStat(name string, fi *FileInfo, lstat, stat *syscall.Stat_t) *F
 	fi.Ino = uint64(stat.Ino)
 	fi.Nlink = uint64(stat.Nlink)
 	fi.Mode = uint32(stat.Mode)
-	fi.Uid = stat.Uid
-	fi.Gid = stat.Gid
+	fi.Uid = int(stat.Uid)
+	fi.Gid = int(stat.Gid)
 	fi.Rdev = uint64(stat.Rdev)
 	fi.Size = uint64(stat.Size)
-	fi.Blksize = uint64(stat.Blksize)
-	fi.Blocks = uint64(stat.Blocks)
-	fi.Atime_ns = uint64(syscall.TimespecToNsec(stat.Atimespec))
-	fi.Mtime_ns = uint64(syscall.TimespecToNsec(stat.Mtimespec))
-	fi.Ctime_ns = uint64(syscall.TimespecToNsec(stat.Ctimespec))
+	fi.Blksize = int64(stat.Blksize)
+	fi.Blocks = stat.Blocks
+	fi.Atime_ns = syscall.TimespecToNsec(stat.Atimespec)
+	fi.Mtime_ns = syscall.TimespecToNsec(stat.Mtimespec)
+	fi.Ctime_ns = syscall.TimespecToNsec(stat.Ctimespec)
 	for i := len(name) - 1; i >= 0; i-- {
 		if name[i] == '/' {
 			name = name[i+1:]
diff --git a/src/pkg/os/stat_linux.go b/src/pkg/os/stat_linux.go
index 5d3b9ee99c0..ebfa1721c0a 100644
--- a/src/pkg/os/stat_linux.go
+++ b/src/pkg/os/stat_linux.go
@@ -12,18 +12,18 @@ func isSymlink(stat *syscall.Stat_t) bool {
 
 func fileInfoFromStat(name string, fi *FileInfo, lstat, stat *syscall.Stat_t) *FileInfo {
 	fi.Dev = stat.Dev
-	fi.Ino = uint64(stat.Ino)
+	fi.Ino = stat.Ino
 	fi.Nlink = uint64(stat.Nlink)
 	fi.Mode = stat.Mode
-	fi.Uid = stat.Uid
-	fi.Gid = stat.Gid
+	fi.Uid = int(stat.Uid)
+	fi.Gid = int(stat.Gid)
 	fi.Rdev = stat.Rdev
-	fi.Size = uint64(stat.Size)
-	fi.Blksize = uint64(stat.Blksize)
-	fi.Blocks = uint64(stat.Blocks)
-	fi.Atime_ns = uint64(syscall.TimespecToNsec(stat.Atim))
-	fi.Mtime_ns = uint64(syscall.TimespecToNsec(stat.Mtim))
-	fi.Ctime_ns = uint64(syscall.TimespecToNsec(stat.Ctim))
+	fi.Size = stat.Size
+	fi.Blksize = int64(stat.Blksize)
+	fi.Blocks = stat.Blocks
+	fi.Atime_ns = syscall.TimespecToNsec(stat.Atim)
+	fi.Mtime_ns = syscall.TimespecToNsec(stat.Mtim)
+	fi.Ctime_ns = syscall.TimespecToNsec(stat.Ctim)
 	for i := len(name) - 1; i >= 0; i-- {
 		if name[i] == '/' {
 			name = name[i+1:]
diff --git a/src/pkg/os/stat_mingw.go b/src/pkg/os/stat_mingw.go
index f2112759b4b..1d8d9b9d740 100644
--- a/src/pkg/os/stat_mingw.go
+++ b/src/pkg/os/stat_mingw.go
@@ -18,7 +18,7 @@ func fileInfoFromStat(name string, fi *FileInfo, lstat, stat *syscall.Stat_t) *F
 	} else {
 		fi.Mode = fi.Mode | 0666
 	}
-	fi.Size = uint64(stat.Windata.FileSizeHigh)<<32 + uint64(stat.Windata.FileSizeLow)
+	fi.Size = int64(stat.Windata.FileSizeHigh)<<32 + uint64(stat.Windata.FileSizeLow)
 	fi.Name = string(syscall.UTF16ToString(stat.Windata.FileName[0:]))
 	fi.FollowedSymlink = false
 	// TODO(brainman): use CreationTime LastAccessTime LastWriteTime to prime following Dir fields
diff --git a/src/pkg/os/types.go b/src/pkg/os/types.go
index 4194ea1772a..0e76e90be03 100644
--- a/src/pkg/os/types.go
+++ b/src/pkg/os/types.go
@@ -18,15 +18,15 @@ type FileInfo struct {
 	Ino             uint64 // inode number.
 	Nlink           uint64 // number of hard links.
 	Mode            uint32 // permission and mode bits.
-	Uid             uint32 // user id of owner.
-	Gid             uint32 // group id of owner.
+	Uid             int    // user id of owner.
+	Gid             int    // group id of owner.
 	Rdev            uint64 // device type for special file.
-	Size            uint64 // length in bytes.
-	Blksize         uint64 // size of blocks, in bytes.
-	Blocks          uint64 // number of blocks allocated for file.
-	Atime_ns        uint64 // access time; nanoseconds since epoch.
-	Mtime_ns        uint64 // modified time; nanoseconds since epoch.
-	Ctime_ns        uint64 // status change time; nanoseconds since epoch.
+	Size            int64  // length in bytes.
+	Blksize         int64  // size of blocks, in bytes.
+	Blocks          int64  // number of blocks allocated for file.
+	Atime_ns        int64  // access time; nanoseconds since epoch.
+	Mtime_ns        int64  // modified time; nanoseconds since epoch.
+	Ctime_ns        int64  // status change time; nanoseconds since epoch.
 	Name            string // name of file as presented to Open.
 	FollowedSymlink bool   // followed a symlink to get this information
 }