diff --git a/src/archive/tar/testdata/ustar.issue12594.tar b/src/archive/tar/testdata/ustar.issue12594.tar
new file mode 100644
index 0000000000..c7910ae9f4
Binary files /dev/null and b/src/archive/tar/testdata/ustar.issue12594.tar differ
diff --git a/src/archive/tar/testdata/writer-big-long.tar b/src/archive/tar/testdata/writer-big-long.tar
index 5960ee8247..52bd748f3b 100644
Binary files a/src/archive/tar/testdata/writer-big-long.tar and b/src/archive/tar/testdata/writer-big-long.tar differ
diff --git a/src/archive/tar/writer.go b/src/archive/tar/writer.go
index bd6e7e5b58..596fb8b9e1 100644
--- a/src/archive/tar/writer.go
+++ b/src/archive/tar/writer.go
@@ -170,9 +170,41 @@ func (tw *Writer) writeHeader(hdr *Header, allowPax bool) error {
 	formatNumeric(ustar.DevMajor(), hdr.Devmajor, paxNone)
 	formatNumeric(ustar.DevMinor(), hdr.Devminor, paxNone)
 
+	// TODO(dsnet): The logic surrounding the prefix field is broken when trying
+	// to encode the header as GNU format. The challenge with the current logic
+	// is that we are unsure what format we are using at any given moment until
+	// we have processed *all* of the fields. The problem is that by the time
+	// all fields have been processed, some work has already been done to handle
+	// each field under the assumption that it is for one given format or
+	// another. In some situations, this causes the Writer to be confused and
+	// encode a prefix field when the format being used is GNU. Thus, producing
+	// an invalid tar file.
+	//
+	// As a short-term fix, we disable the logic to use the prefix field, which
+	// will force the badly generated GNU files to become encoded as being
+	// the PAX format.
+	//
+	// As an alternative fix, we could hard-code preferPax to be true. However,
+	// this is problematic for the following reasons:
+	//	* The preferPax functionality is not tested at all.
+	//	* This can result in headers that try to use both the GNU and PAX
+	//	features at the same time, which is also wrong.
+	//
+	// The proper fix for this is to use a two-pass method:
+	//	* The first pass simply determines what set of formats can possibly
+	//	encode the given header.
+	//	* The second pass actually encodes the header as that given format
+	//	without worrying about violating the format.
+	//
+	// See the following:
+	//	https://golang.org/issue/12594
+	//	https://golang.org/issue/17630
+	//	https://golang.org/issue/9683
+	const usePrefix = false
+
 	// try to use a ustar header when only the name is too long
 	_, paxPathUsed := paxHeaders[paxPath]
-	if !tw.preferPax && len(paxHeaders) == 1 && paxPathUsed {
+	if usePrefix && !tw.preferPax && len(paxHeaders) == 1 && paxPathUsed {
 		prefix, suffix, ok := splitUSTARPath(hdr.Name)
 		if ok {
 			// Since we can encode in USTAR format, disable PAX header.
diff --git a/src/archive/tar/writer_test.go b/src/archive/tar/writer_test.go
index 678254dbc1..d88b8f41ca 100644
--- a/src/archive/tar/writer_test.go
+++ b/src/archive/tar/writer_test.go
@@ -133,9 +133,13 @@ func TestWriter(t *testing.T) {
 			contents: strings.Repeat("\x00", 4<<10),
 		}},
 	}, {
-		// The truncated test file was produced using these commands:
-		//   dd if=/dev/zero bs=1048576 count=16384 > (longname/)*15 /16gig.txt
-		//   tar -b 1 -c -f- (longname/)*15 /16gig.txt | dd bs=512 count=8 > writer-big-long.tar
+		// This truncated file was produced using this library.
+		// It was verified to work with GNU tar 1.27.1 and BSD tar 3.1.2.
+		//  dd if=/dev/zero bs=1G count=16 >> writer-big-long.tar
+		//  gnutar -xvf writer-big-long.tar
+		//  bsdtar -xvf writer-big-long.tar
+		//
+		// This file is in PAX format.
 		file: "testdata/writer-big-long.tar",
 		entries: []*entry{{
 			header: &Header{
@@ -153,9 +157,15 @@ func TestWriter(t *testing.T) {
 			contents: strings.Repeat("\x00", 4<<10),
 		}},
 	}, {
-		// This file was produced using gnu tar 1.17
-		// gnutar  -b 4 --format=ustar (longname/)*15 + file.txt
-		file: "testdata/ustar.tar",
+		// TODO(dsnet): The Writer output should match the following file.
+		// To fix an issue (see https://golang.org/issue/12594), we disabled
+		// prefix support, which alters the generated output.
+		/*
+			// This file was produced using gnu tar 1.17
+			// gnutar  -b 4 --format=ustar (longname/)*15 + file.txt
+			file: "testdata/ustar.tar"
+		*/
+		file: "testdata/ustar.issue12594.tar", // This is a valid tar file, but not expected
 		entries: []*entry{{
 			header: &Header{
 				Name:     strings.Repeat("longname/", 15) + "file.txt",
@@ -586,3 +596,52 @@ func TestSplitUSTARPath(t *testing.T) {
 		}
 	}
 }
+
+// TestIssue12594 tests that the Writer does not attempt to populate the prefix
+// field when encoding a header in the GNU format. The prefix field is valid
+// in USTAR and PAX, but not GNU.
+func TestIssue12594(t *testing.T) {
+	names := []string{
+		"0/1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/file.txt",
+		"0/1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/31/32/33/file.txt",
+		"0/1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/31/32/333/file.txt",
+		"0/1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/31/32/33/34/35/36/37/38/39/40/file.txt",
+		"0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000/file.txt",
+		"/home/support/.openoffice.org/3/user/uno_packages/cache/registry/com.sun.star.comp.deployment.executable.PackageRegistryBackend",
+	}
+
+	for i, name := range names {
+		var b bytes.Buffer
+
+		tw := NewWriter(&b)
+		if err := tw.WriteHeader(&Header{
+			Name: name,
+			Uid:  1 << 25, // Prevent USTAR format
+		}); err != nil {
+			t.Errorf("test %d, unexpected WriteHeader error: %v", i, err)
+		}
+		if err := tw.Close(); err != nil {
+			t.Errorf("test %d, unexpected Close error: %v", i, err)
+		}
+
+		// The prefix field should never appear in the GNU format.
+		var blk block
+		copy(blk[:], b.Bytes())
+		prefix := string(blk.USTAR().Prefix())
+		if i := strings.IndexByte(prefix, 0); i >= 0 {
+			prefix = prefix[:i] // Truncate at the NUL terminator
+		}
+		if blk.GetFormat() == formatGNU && len(prefix) > 0 && strings.HasPrefix(name, prefix) {
+			t.Errorf("test %d, found prefix in GNU format: %s", i, prefix)
+		}
+
+		tr := NewReader(&b)
+		hdr, err := tr.Next()
+		if err != nil {
+			t.Errorf("test %d, unexpected Next error: %v", i, err)
+		}
+		if hdr.Name != name {
+			t.Errorf("test %d, hdr.Name = %s, want %s", i, hdr.Name, name)
+		}
+	}
+}