diff --git a/ulisp-arm.ino b/ulisp-arm.ino
index 291a848..81bd04a 100644
--- a/ulisp-arm.ino
+++ b/ulisp-arm.ino
@@ -1,5 +1,5 @@
-/* uLisp ARM Version 3.5a - www.ulisp.com
-   David Johnson-Davies - www.technoblogy.com - 19th March 2021
+/* uLisp ARM Version 3.6 - www.ulisp.com
+   David Johnson-Davies - www.technoblogy.com - 4th April 2021
 
    Licensed under the MIT license: https://opensource.org/licenses/MIT
 */
@@ -330,7 +330,7 @@ char LastChar = 0;
 char LastPrint = 0;
 
 // Flags
-enum flag { PRINTREADABLY, RETURNFLAG, ESCAPE, EXITEDITOR, LIBRARYLOADED, NOESC };
+enum flag { PRINTREADABLY, RETURNFLAG, ESCAPE, EXITEDITOR, LIBRARYLOADED, NOESC, NOECHO };
 volatile uint8_t Flags = 0b00001; // PRINTREADABLY set by default
 
 // Forward references
@@ -795,7 +795,7 @@ int loadimage (object *arg) {
   else error(LOADIMAGE, PSTR("illegal argument"), arg);
   if (!file) error2(LOADIMAGE, PSTR("problem loading from SD card"));
   SDReadInt(file);
-  int imagesize = SDReadInt(file);
+  unsigned int imagesize = SDReadInt(file);
   GlobalEnv = (object *)SDReadInt(file);
   GCStack = (object *)SDReadInt(file);
   #if SYMBOLTABLESIZE > BUFFERSIZE
@@ -804,7 +804,7 @@ int loadimage (object *arg) {
   for (int i=0; i<SymbolUsed; i++) SymbolTable[i] = file.read();
   #endif
   for (int i=0; i<CODESIZE; i++) MyCode[i] = file.read();
-  for (int i=0; i<imagesize; i++) {
+  for (unsigned int i=0; i<imagesize; i++) {
     object *obj = &Workspace[i];
     car(obj) = (object *)SDReadInt(file);
     cdr(obj) = (object *)SDReadInt(file);
@@ -816,7 +816,7 @@ int loadimage (object *arg) {
   if (!FlashSetup()) error2(LOADIMAGE, PSTR("no DataFlash found."));
   FlashBeginRead();
   FlashReadInt(); // Skip eval address
-  int imagesize = FlashReadInt();
+  unsigned int imagesize = FlashReadInt();
   if (imagesize == 0 || imagesize == 0xFFFFFFFF) error2(LOADIMAGE, PSTR("no saved image"));
   GlobalEnv = (object *)FlashReadInt();
   GCStack = (object *)FlashReadInt();
@@ -826,7 +826,7 @@ int loadimage (object *arg) {
   for (int i=0; i<SymbolUsed; i++) SymbolTable[i] = FlashReadByte();
   #endif
   for (int i=0; i<CODESIZE; i++) MyCode[i] = FlashReadByte();
-  for (int i=0; i<imagesize; i++) {
+  for (unsigned int i=0; i<imagesize; i++) {
     object *obj = &Workspace[i];
     car(obj) = (object *)FlashReadInt();
     cdr(obj) = (object *)FlashReadInt();
@@ -2506,7 +2506,7 @@ object *sp_defcode (object *args, object *env) {
   object *globals = GlobalEnv;
   while (globals != NULL) {
     object *pair = car(globals);
-    if (pair != NULL && car(pair) != var) { // Exclude me if I already exist
+    if (pair != NULL && car(pair) != var && consp(cdr(pair))) { // Exclude me if I already exist
       object *codeid = second(pair);
       if (codeid->type == CODE) {
         codesize = codesize + endblock(codeid) - startblock(codeid);
@@ -2526,7 +2526,7 @@ object *sp_defcode (object *args, object *env) {
     globals = GlobalEnv;
     while (globals != NULL) {
       object *pair = car(globals);
-      if (pair != NULL && car(pair) != var) { // Exclude me if I already exist
+      if (pair != NULL && car(pair) != var && consp(cdr(pair))) { // Exclude me if I already exist
         object *codeid = second(pair);
         if (codeid->type == CODE) {
           if (startblock(codeid) < smallest && startblock(codeid) >= origin) {
@@ -3952,7 +3952,7 @@ object *fn_pinmode (object *args, object *env) {
   int pin = checkinteger(PINMODE, first(args));
   PinMode pm = INPUT;
   object *arg = second(args);
-  if (keywordp(arg)) pm = checkkeyword(PINMODE, arg);
+  if (keywordp(arg)) pm = (PinMode)checkkeyword(PINMODE, arg);
   else if (integerp(arg)) {
     int mode = arg->integer;
     if (mode == 1) pm = OUTPUT; else if (mode == 2) pm = INPUT_PULLUP;
@@ -5150,7 +5150,9 @@ object *eval (object *form, object *env) {
     error(0, PSTR("undefined"), form);
   }
 
+  #if defined(CODESIZE)
   if (form->type == CODE) error2(0, PSTR("can't evaluate CODE header"));
+  #endif
 
   // It's a list
   object *function = car(form);
@@ -5603,9 +5605,10 @@ int gserial () {
   WritePtr = 0;
   return '\n';
 #else
-  while (!Serial.available());
+  unsigned long start = millis();
+  while (!Serial.available()) if (millis() - start > 1000) clrflag(NOECHO);
   char temp = Serial.read();
-  if (temp != '\n') pserial(temp);
+  if (temp != '\n' && !tstflag(NOECHO)) pserial(temp);
   return temp;
 #endif
 }
@@ -5615,8 +5618,8 @@ object *nextitem (gfun_t gfun) {
   while(issp(ch)) ch = gfun();
 
   if (ch == ';') {
-    while(ch != '(') ch = gfun();
-    ch = '(';
+    do { ch = gfun(); if (ch == ';' || ch == '(') setflag(NOECHO); }
+    while(ch != '(');
   }
   if (ch == '\n') ch = gfun();
   if (ch == -1) return nil;
@@ -5795,7 +5798,7 @@ void setup () {
   initenv();
   initsleep();
   initgfx();
-  pfstring(PSTR("uLisp 3.5 "), pserial); pln(pserial);
+  pfstring(PSTR("uLisp 3.6 "), pserial); pln(pserial);
 }
 
 // Read/Evaluate/Print loop
@@ -5846,4 +5849,4 @@ void loop () {
   if (!tstflag(LIBRARYLOADED)) { setflag(LIBRARYLOADED); loadfromlibrary(NULL); }
   #endif
   repl(NULL);
-}
+}
\ No newline at end of file