diff --git a/src/ebusd/mainloop.cpp b/src/ebusd/mainloop.cpp
index 7c9234bb..b24a05b6 100755
--- a/src/ebusd/mainloop.cpp
+++ b/src/ebusd/mainloop.cpp
@@ -713,16 +713,16 @@ result_t MainLoop::executeRead(const vector<string>& args, const string& levels,
       }
       circuit = args[argPos];
     } else if (args[argPos] == "-s" || args[argPos] == "-d") {
+      bool dest = args[argPos] == "-d";
       argPos++;
       if (argPos >= args.size()) {
         argPos = 0;  // print usage
         break;
       }
-      bool dest = args[argPos] == "-d";
       result_t ret;
       symbol_t address = (symbol_t)parseInt(args[argPos].c_str(), 16, 0, 0xff, &ret);
-      if (ret != RESULT_OK || !isValidAddress(address, dest) || dest == isMaster(address)) {
-        return RESULT_ERR_INVALID_ADDR;
+      if (ret != RESULT_OK || !isValidAddress(address, dest) || (dest == isMaster(address))) {
+        return RESULT_ERR_INVALID_ADDR; // deny send from slave address and to master addresses
       }
       if (dest) {
         dstAddress = address;
@@ -940,16 +940,16 @@ result_t MainLoop::executeWrite(const vector<string>& args, const string levels,
     if (args[argPos] == "-h") {
       hex = true;
     } else if (args[argPos] == "-s" || args[argPos] == "-d") {
+      bool dest = args[argPos] == "-d";
       argPos++;
       if (argPos >= args.size()) {
         argPos = 0;  // print usage
         break;
       }
-      bool dest = args[argPos] == "-d";
       result_t ret;
       symbol_t address = (symbol_t)parseInt(args[argPos].c_str(), 16, 0, 0xff, &ret);
-      if (ret != RESULT_OK || !isValidAddress(address, dest) || dest == isMaster(address)) {
-        return RESULT_ERR_INVALID_ADDR;
+      if (ret != RESULT_OK || !isValidAddress(address, dest) || (!dest && !isMaster(address))) {
+        return RESULT_ERR_INVALID_ADDR; // deny send from slave address
       }
       if (dest) {
         dstAddress = address;