diff --git a/vlib/x/websocket/message.v b/vlib/x/websocket/message.v
index bb7b58b310..8dcb5fa0d4 100644
--- a/vlib/x/websocket/message.v
+++ b/vlib/x/websocket/message.v
@@ -1,7 +1,6 @@
 module websocket
 
 import encoding.utf8
-import math
 
 const (
 	header_len_offset           = 2 // offset for lengthpart of websocket header
@@ -254,7 +253,7 @@ pub fn (mut ws Client) parse_frame_header() ?Frame {
 		if frame.payload_len == 126 && bytes_read == u64(extended_payload16_end_byte) {
 			frame.header_len += 2
 			frame.payload_len = 0
-			frame.payload_len |= (buffer[2] * int(math.pow(2, 8)))
+			frame.payload_len |= buffer[2] << 8
 			frame.payload_len |= buffer[3]
 			frame.frame_size = frame.header_len + frame.payload_len
 			if !frame.has_mask {
@@ -263,15 +262,17 @@ pub fn (mut ws Client) parse_frame_header() ?Frame {
 		}
 		if frame.payload_len == 127 && bytes_read == u64(extended_payload64_end_byte) {
 			frame.header_len += 8
-			frame.payload_len = 0
-			frame.payload_len |= (buffer[2] * int(math.pow(2, 56)))
-			frame.payload_len |= (buffer[3] * int(math.pow(2, 48)))
-			frame.payload_len |= (buffer[4] * int(math.pow(2, 40)))
-			frame.payload_len |= (buffer[5] * int(math.pow(2, 32)))
-			frame.payload_len |= (buffer[6] * int(math.pow(2, 24)))
-			frame.payload_len |= (buffer[7] * int(math.pow(2, 16)))
-			frame.payload_len |= (buffer[8] * int(math.pow(2, 8)))
-			frame.payload_len |= buffer[9]
+			// these shift operators needs 64 bit on clang with -prod flag
+			mut payload_len := u64(0)
+			payload_len |= buffer[2] << 56
+			payload_len |= buffer[3] << 48
+			payload_len |= buffer[4] << 40
+			payload_len |= buffer[5] << 32
+			payload_len |= buffer[6] << 24
+			payload_len |= buffer[7] << 16
+			payload_len |= buffer[8] << 8
+			payload_len |= buffer[9]
+			frame.payload_len = int(payload_len)
 			if !frame.has_mask {
 				break
 			}