diff --git a/src/io/io.go b/src/io/io.go
index 27482de62e..3999a385c6 100644
--- a/src/io/io.go
+++ b/src/io/io.go
@@ -300,6 +300,7 @@ func WriteString(w Writer, s string) (n int, err error) {
 // ReadAtLeast returns ErrUnexpectedEOF.
 // If min is greater than the length of buf, ReadAtLeast returns ErrShortBuffer.
 // On return, n >= min if and only if err == nil.
+// If r returns an error having read at least min bytes, the error is dropped.
 func ReadAtLeast(r Reader, buf []byte, min int) (n int, err error) {
 	if len(buf) < min {
 		return 0, ErrShortBuffer
@@ -323,6 +324,7 @@ func ReadAtLeast(r Reader, buf []byte, min int) (n int, err error) {
 // If an EOF happens after reading some but not all the bytes,
 // ReadFull returns ErrUnexpectedEOF.
 // On return, n == len(buf) if and only if err == nil.
+// If r returns an error having read at least len(buf) bytes, the error is dropped.
 func ReadFull(r Reader, buf []byte) (n int, err error) {
 	return ReadAtLeast(r, buf, len(buf))
 }