diff --git a/src/HomeSpan.cpp b/src/HomeSpan.cpp
index 003601e..62ee37c 100644
--- a/src/HomeSpan.cpp
+++ b/src/HomeSpan.cpp
@@ -2279,7 +2279,7 @@ boolean SpanPoint::get(void *dataBuf){
 
 ///////////////////////////////
 
-boolean SpanPoint::send(void *data){
+boolean SpanPoint::send(const void *data){
 
   if(sendSize==0)
     return(false);
diff --git a/src/HomeSpan.h b/src/HomeSpan.h
index 3312d42..627bf96 100644
--- a/src/HomeSpan.h
+++ b/src/HomeSpan.h
@@ -784,7 +784,7 @@ class SpanPoint {
   static void setPassword(const char *pwd){init(pwd);};      
   static void setChannelMask(uint16_t mask);  
   boolean get(void *dataBuf);
-  boolean send(void *data);
+  boolean send(const void *data);
   uint32_t time(){return(millis()-receiveTime);}
 };