diff --git a/src/internal/poll/fd_windows.go b/src/internal/poll/fd_windows.go
index 187908bc83..1114d66a7a 100644
--- a/src/internal/poll/fd_windows.go
+++ b/src/internal/poll/fd_windows.go
@@ -225,6 +225,10 @@ func (s *ioSrv) ExecIO(o *operation, submit func(o *operation) error) (int, erro
 		// All is good. Extract our IO results and return.
 		if o.errno != 0 {
 			err = syscall.Errno(o.errno)
+			// More data available. Return back the size of received data.
+			if err == syscall.ERROR_MORE_DATA || err == syscall.WSAEMSGSIZE {
+				return int(o.qty), err
+			}
 			return 0, err
 		}
 		return int(o.qty), nil
diff --git a/src/net/net.go b/src/net/net.go
index 3ad91036e7..5182c0de95 100644
--- a/src/net/net.go
+++ b/src/net/net.go
@@ -303,20 +303,23 @@ func (c *conn) File() (f *os.File, err error) {
 // Multiple goroutines may invoke methods on a PacketConn simultaneously.
 type PacketConn interface {
 	// ReadFrom reads a packet from the connection,
-	// copying the payload into b. It returns the number of
-	// bytes copied into b and the return address that
+	// copying the payload into p. It returns the number of
+	// bytes copied into p and the return address that
 	// was on the packet.
+	// It returns the number of bytes read (0 <= n <= len(p))
+	// and any error encountered. Callers should always process
+	// the n > 0 bytes returned before considering the error err.
 	// ReadFrom can be made to time out and return
 	// an Error with Timeout() == true after a fixed time limit;
 	// see SetDeadline and SetReadDeadline.
-	ReadFrom(b []byte) (n int, addr Addr, err error)
+	ReadFrom(p []byte) (n int, addr Addr, err error)
 
-	// WriteTo writes a packet with payload b to addr.
+	// WriteTo writes a packet with payload p to addr.
 	// WriteTo can be made to time out and return
 	// an Error with Timeout() == true after a fixed time limit;
 	// see SetDeadline and SetWriteDeadline.
 	// On packet-oriented connections, write timeouts are rare.
-	WriteTo(b []byte, addr Addr) (n int, err error)
+	WriteTo(p []byte, addr Addr) (n int, err error)
 
 	// Close closes the connection.
 	// Any blocked ReadFrom or WriteTo operations will be unblocked and return errors.
diff --git a/src/net/timeout_test.go b/src/net/timeout_test.go
index 9de7801ad1..0ecf5a6d25 100644
--- a/src/net/timeout_test.go
+++ b/src/net/timeout_test.go
@@ -482,7 +482,7 @@ func TestReadFromTimeout(t *testing.T) {
 					time.Sleep(tt.timeout / 3)
 					continue
 				}
-				if n != 0 {
+				if nerr, ok := err.(Error); ok && nerr.Timeout() && n != 0 {
 					t.Fatalf("#%d/%d: read %d; want 0", i, j, n)
 				}
 				break
diff --git a/src/net/udpsock_test.go b/src/net/udpsock_test.go
index 4ae014c01d..d34c545096 100644
--- a/src/net/udpsock_test.go
+++ b/src/net/udpsock_test.go
@@ -398,9 +398,56 @@ func TestUDPZeroByteBuffer(t *testing.T) {
 		switch err {
 		case nil: // ReadFrom succeeds
 		default: // Read may timeout, it depends on the platform
-			if nerr, ok := err.(Error); (!ok || !nerr.Timeout()) && runtime.GOOS != "windows" { // Windows returns WSAEMSGSIZ
+			if nerr, ok := err.(Error); (!ok || !nerr.Timeout()) && runtime.GOOS != "windows" { // Windows returns WSAEMSGSIZE
 				t.Fatal(err)
 			}
 		}
 	}
 }
+
+func TestUDPReadSizeError(t *testing.T) {
+	switch runtime.GOOS {
+	case "nacl", "plan9":
+		t.Skipf("not supported on %s", runtime.GOOS)
+	}
+
+	c1, err := newLocalPacketListener("udp")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c1.Close()
+
+	c2, err := Dial("udp", c1.LocalAddr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c2.Close()
+
+	b1 := []byte("READ SIZE ERROR TEST")
+	for _, genericRead := range []bool{false, true} {
+		n, err := c2.Write(b1)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if n != len(b1) {
+			t.Errorf("got %d; want %d", n, len(b1))
+		}
+		c1.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
+		b2 := make([]byte, len(b1)-1)
+		if genericRead {
+			n, err = c1.(Conn).Read(b2)
+		} else {
+			n, _, err = c1.ReadFrom(b2)
+		}
+		switch err {
+		case nil: // ReadFrom succeeds
+		default: // Read may timeout, it depends on the platform
+			if nerr, ok := err.(Error); (!ok || !nerr.Timeout()) && runtime.GOOS != "windows" { // Windows returns WSAEMSGSIZE
+				t.Fatal(err)
+			}
+		}
+		if n != len(b1)-1 {
+			t.Fatalf("got %d; want %d", n, len(b1)-1)
+		}
+	}
+}
diff --git a/src/syscall/types_windows.go b/src/syscall/types_windows.go
index bc9bd4dbd8..59bfe5d642 100644
--- a/src/syscall/types_windows.go
+++ b/src/syscall/types_windows.go
@@ -27,6 +27,7 @@ const (
 	ERROR_NOT_FOUND           Errno = 1168
 	ERROR_PRIVILEGE_NOT_HELD  Errno = 1314
 	WSAEACCES                 Errno = 10013
+	WSAEMSGSIZE               Errno = 10040
 	WSAECONNABORTED           Errno = 10053
 	WSAECONNRESET             Errno = 10054
 )