diff --git a/src/os/file.go b/src/os/file.go
index 10aed03b965975..ea81a8ba634e7b 100644
--- a/src/os/file.go
+++ b/src/os/file.go
@@ -158,11 +158,19 @@ func (f *File) ReadFrom(r io.Reader) (n int64, err error) {
 }
 
 func genericReadFrom(f *File, r io.Reader) (int64, error) {
-	return io.Copy(onlyWriter{f}, r)
+	return io.Copy(fileWithoutReadFrom{f}, r)
 }
 
-type onlyWriter struct {
-	io.Writer
+// fileWithoutReadFrom implements all the methods of *File other
+// than ReadFrom. This is used to permit ReadFrom to call io.Copy
+// without leading to a recursive call to ReadFrom.
+type fileWithoutReadFrom struct {
+	*File
+}
+
+// This ReadFrom method hides the *File ReadFrom method.
+func (fileWithoutReadFrom) ReadFrom(fileWithoutReadFrom) {
+	panic("unreachable")
 }
 
 // Write writes len(b) bytes from b to the File.