4 files changed, 8 insertions, 5 deletions
diff --git a/src/debug/pe/file.go b/src/debug/pe/file.go
index ef4ae352fe..87f225cb39 100644
--- a/src/debug/pe/file.go
+++ b/src/debug/pe/file.go
@@ -13,6 +13,9 @@ import (
 	"os"
 )
 
+// Avoid use of post-Go 1.4 io features, to make safe for toolchain bootstrap.
+const seekStart = 0
+
 // A File represents an open PE file.
 type File struct {
 	FileHeader
@@ -80,7 +83,7 @@ func NewFile(r io.ReaderAt) (*File, error) {
 	} else {
 		base = int64(0)
 	}
-	sr.Seek(base, io.SeekStart)
+	sr.Seek(base, seekStart)
 	if err := binary.Read(sr, binary.LittleEndian, &f.FileHeader); err != nil {
 		return nil, err
 	}
@@ -109,7 +112,7 @@ func NewFile(r io.ReaderAt) (*File, error) {
 	}
 
 	// Read optional header.
-	sr.Seek(base, io.SeekStart)
+	sr.Seek(base, seekStart)
 	if err := binary.Read(sr, binary.LittleEndian, &f.FileHeader); err != nil {
 		return nil, err
 	}
diff --git a/src/debug/pe/section.go b/src/debug/pe/section.go
index 5d881577d3..b641158ecc 100644
--- a/src/debug/pe/section.go
+++ b/src/debug/pe/section.go
@@ -53,7 +53,7 @@ func readRelocs(sh *SectionHeader, r io.ReadSeeker) ([]Reloc, error) {
 	if sh.NumberOfRelocations <= 0 {
 		return nil, nil
 	}
-	_, err := r.Seek(int64(sh.PointerToRelocations), io.SeekStart)
+	_, err := r.Seek(int64(sh.PointerToRelocations), seekStart)
 	if err != nil {
 		return nil, fmt.Errorf("fail to seek to %q section relocations: %v", sh.Name, err)
 	}
diff --git a/src/debug/pe/string.go b/src/debug/pe/string.go
index 357fcf4343..0155adf9f0 100644
--- a/src/debug/pe/string.go
+++ b/src/debug/pe/string.go
@@ -28,7 +28,7 @@ func readStringTable(fh *FileHeader, r io.ReadSeeker) (StringTable, error) {
 		return nil, nil
 	}
 	offset := fh.PointerToSymbolTable + COFFSymbolSize*fh.NumberOfSymbols
-	_, err := r.Seek(int64(offset), io.SeekStart)
+	_, err := r.Seek(int64(offset), seekStart)
 	if err != nil {
 		return nil, fmt.Errorf("fail to seek to string table: %v", err)
 	}
diff --git a/src/debug/pe/symbol.go b/src/debug/pe/symbol.go
index 3cf5a101e7..b7d5d09bcf 100644
--- a/src/debug/pe/symbol.go
+++ b/src/debug/pe/symbol.go
@@ -26,7 +26,7 @@ func readCOFFSymbols(fh *FileHeader, r io.ReadSeeker) ([]COFFSymbol, error) {
 	if fh.NumberOfSymbols <= 0 {
 		return nil, nil
 	}
-	_, err := r.Seek(int64(fh.PointerToSymbolTable), io.SeekStart)
+	_, err := r.Seek(int64(fh.PointerToSymbolTable), seekStart)
 	if err != nil {
 		return nil, fmt.Errorf("fail to seek to symbol table: %v", err)
 	}