diff --git a/core/er-coap-13/er-coap-13.h b/core/er-coap-13/er-coap-13.h
index 3fbe540a8..beca54432 100644
--- a/core/er-coap-13/er-coap-13.h
+++ b/core/er-coap-13/er-coap-13.h
@@ -58,7 +58,7 @@
 #define COAP_MAX_RETRANSMIT                  4
 #define COAP_ACK_RANDOM_FACTOR               1.5
 
-#define COAP_MAX_TRANSMIT_WAIT               ((COAP_RESPONSE_TIMEOUT * ((2 ^ (COAP_MAX_RETRANSMIT + 1)) - 1) * COAP_ACK_RANDOM_FACTOR))
+#define COAP_MAX_TRANSMIT_WAIT               ((COAP_RESPONSE_TIMEOUT * ( (1 << (COAP_MAX_RETRANSMIT + 1) ) - 1) * COAP_ACK_RANDOM_FACTOR))
 
 #define COAP_HEADER_LEN                      4 /* | version:0x03 type:0x0C tkl:0xF0 | code | mid:0x00FF | mid:0xFF00 | */
 #define COAP_ETAG_LEN                        8 /* The maximum number of bytes for the ETag */