diff --git a/ChangeLog b/ChangeLog
index ea9cf447b5..88ca037305 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -12,6 +12,7 @@
             RAK5010: switch to 1.8v internal voltage (was 3.3v) to make GSM comms reliable, upgrade BG96 module
             RAK5010: Compile in TLS/HTTPS support
             Bangle.js: Fix issue where if non-fullscreen notification was visible and Bangle.js reset, screen was off-center
+            Fix for issue with pretokenised code not creating correct text string for reserved words, eg {undefined:1}
 
      2v10 : Bangle.js: Improved HRM calculations - swapped autocorrelation for bandpass filter
             Bangle.js: Significantly improved step counting algorithm using bandpass filter (fix #1846)
diff --git a/src/jslex.c b/src/jslex.c
index 44b231402d..cd4bba77a9 100644
--- a/src/jslex.c
+++ b/src/jslex.c
@@ -733,6 +733,83 @@ void jslFunctionCharAsString(unsigned char ch, char *str, size_t len) {
   }
 }
 
+const char* jslReservedWordAsString(int token) {
+  static const char tokenNames[] =
+      /* LEX_EQUAL      :   */ "==\0"
+      /* LEX_TYPEEQUAL  :   */ "===\0"
+      /* LEX_NEQUAL     :   */ "!=\0"
+      /* LEX_NTYPEEQUAL :   */ "!==\0"
+      /* LEX_LEQUAL    :    */ "<=\0"
+      /* LEX_LSHIFT     :   */ "<<\0"
+      /* LEX_LSHIFTEQUAL :  */ "<<=\0"
+      /* LEX_GEQUAL      :  */ ">=\0"
+      /* LEX_RSHIFT      :  */ ">>\0"
+      /* LEX_RSHIFTUNSIGNED */ ">>>\0"
+      /* LEX_RSHIFTEQUAL :  */ ">>=\0"
+      /* LEX_RSHIFTUNSIGNEDEQUAL */ ">>>=\0"
+      /* LEX_PLUSEQUAL   :  */ "+=\0"
+      /* LEX_MINUSEQUAL  :  */ "-=\0"
+      /* LEX_PLUSPLUS :     */ "++\0"
+      /* LEX_MINUSMINUS     */ "--\0"
+      /* LEX_MULEQUAL :     */ "*=\0"
+      /* LEX_DIVEQUAL :     */ "/=\0"
+      /* LEX_MODEQUAL :     */ "%=\0"
+      /* LEX_ANDEQUAL :     */ "&=\0"
+      /* LEX_ANDAND :       */ "&&\0"
+      /* LEX_OREQUAL :      */ "|=\0"
+      /* LEX_OROR :         */ "||\0"
+      /* LEX_XOREQUAL :     */ "^=\0"
+      /* LEX_ARROW_FUNCTION */ "=>\0"
+
+      // reserved words
+      /*LEX_R_IF :       */ "if\0"
+      /*LEX_R_ELSE :     */ "else\0"
+      /*LEX_R_DO :       */ "do\0"
+      /*LEX_R_WHILE :    */ "while\0"
+      /*LEX_R_FOR :      */ "for\0"
+      /*LEX_R_BREAK :    */ "break\0"
+      /*LEX_R_CONTINUE   */ "continue\0"
+      /*LEX_R_FUNCTION   */ "function\0"
+      /*LEX_R_RETURN     */ "return\0"
+      /*LEX_R_VAR :      */ "var\0"
+      /*LEX_R_LET :      */ "let\0"
+      /*LEX_R_CONST :    */ "const\0"
+      /*LEX_R_THIS :     */ "this\0"
+      /*LEX_R_THROW :    */ "throw\0"
+      /*LEX_R_TRY :      */ "try\0"
+      /*LEX_R_CATCH :    */ "catch\0"
+      /*LEX_R_FINALLY :  */ "finally\0"
+      /*LEX_R_TRUE :     */ "true\0"
+      /*LEX_R_FALSE :    */ "false\0"
+      /*LEX_R_NULL :     */ "null\0"
+      /*LEX_R_UNDEFINED  */ "undefined\0"
+      /*LEX_R_NEW :      */ "new\0"
+      /*LEX_R_IN :       */ "in\0"
+      /*LEX_R_INSTANCEOF */ "instanceof\0"
+      /*LEX_R_SWITCH     */ "switch\0"
+      /*LEX_R_CASE       */ "case\0"
+      /*LEX_R_DEFAULT    */ "default\0"
+      /*LEX_R_DELETE     */ "delete\0"
+      /*LEX_R_TYPEOF :   */ "typeof\0"
+      /*LEX_R_VOID :     */ "void\0"
+      /*LEX_R_DEBUGGER : */ "debugger\0"
+      /*LEX_R_CLASS :    */ "class\0"
+      /*LEX_R_EXTENDS :  */ "extends\0"
+      /*LEX_R_SUPER :  */   "super\0"
+      /*LEX_R_STATIC :   */ "static\0"
+      /*LEX_R_OF    :   */  "of\0"
+      ;
+  unsigned int p = 0;
+  int n = token-_LEX_OPERATOR_START;
+  while (n>0 && p<sizeof(tokenNames)) {
+    while (tokenNames[p] && p<sizeof(tokenNames)) p++;
+    p++; // skip the zero
+    n--; // next token
+  }
+  assert(n==0);
+  return &tokenNames[p];
+}
+
 void jslTokenAsString(int token, char *str, size_t len) {
   assert(len>28); // size of largest string
   // see JS_ERROR_TOKEN_BUF_SIZE
@@ -761,80 +838,7 @@ void jslTokenAsString(int token, char *str, size_t len) {
   case 255 : strcpy(str, "[ERASED]"); return;
   }
   if (token>=_LEX_OPERATOR_START && token<=_LEX_R_LIST_END) {
-    const char tokenNames[] =
-        /* LEX_EQUAL      :   */ "==\0"
-        /* LEX_TYPEEQUAL  :   */ "===\0"
-        /* LEX_NEQUAL     :   */ "!=\0"
-        /* LEX_NTYPEEQUAL :   */ "!==\0"
-        /* LEX_LEQUAL    :    */ "<=\0"
-        /* LEX_LSHIFT     :   */ "<<\0"
-        /* LEX_LSHIFTEQUAL :  */ "<<=\0"
-        /* LEX_GEQUAL      :  */ ">=\0"
-        /* LEX_RSHIFT      :  */ ">>\0"
-        /* LEX_RSHIFTUNSIGNED */ ">>>\0"
-        /* LEX_RSHIFTEQUAL :  */ ">>=\0"
-        /* LEX_RSHIFTUNSIGNEDEQUAL */ ">>>=\0"
-        /* LEX_PLUSEQUAL   :  */ "+=\0"
-        /* LEX_MINUSEQUAL  :  */ "-=\0"
-        /* LEX_PLUSPLUS :     */ "++\0"
-        /* LEX_MINUSMINUS     */ "--\0"
-        /* LEX_MULEQUAL :     */ "*=\0"
-        /* LEX_DIVEQUAL :     */ "/=\0"
-        /* LEX_MODEQUAL :     */ "%=\0"
-        /* LEX_ANDEQUAL :     */ "&=\0"
-        /* LEX_ANDAND :       */ "&&\0"
-        /* LEX_OREQUAL :      */ "|=\0"
-        /* LEX_OROR :         */ "||\0"
-        /* LEX_XOREQUAL :     */ "^=\0"
-        /* LEX_ARROW_FUNCTION */ "=>\0"
-
-        // reserved words
-        /*LEX_R_IF :       */ "if\0"
-        /*LEX_R_ELSE :     */ "else\0"
-        /*LEX_R_DO :       */ "do\0"
-        /*LEX_R_WHILE :    */ "while\0"
-        /*LEX_R_FOR :      */ "for\0"
-        /*LEX_R_BREAK :    */ "break\0"
-        /*LEX_R_CONTINUE   */ "continue\0"
-        /*LEX_R_FUNCTION   */ "function\0"
-        /*LEX_R_RETURN     */ "return\0"
-        /*LEX_R_VAR :      */ "var\0"
-        /*LEX_R_LET :      */ "let\0"
-        /*LEX_R_CONST :    */ "const\0"
-        /*LEX_R_THIS :     */ "this\0"
-        /*LEX_R_THROW :    */ "throw\0"
-        /*LEX_R_TRY :      */ "try\0"
-        /*LEX_R_CATCH :    */ "catch\0"
-        /*LEX_R_FINALLY :  */ "finally\0"
-        /*LEX_R_TRUE :     */ "true\0"
-        /*LEX_R_FALSE :    */ "false\0"
-        /*LEX_R_NULL :     */ "null\0"
-        /*LEX_R_UNDEFINED  */ "undefined\0"
-        /*LEX_R_NEW :      */ "new\0"
-        /*LEX_R_IN :       */ "in\0"
-        /*LEX_R_INSTANCEOF */ "instanceof\0"
-        /*LEX_R_SWITCH     */ "switch\0"
-        /*LEX_R_CASE       */ "case\0"
-        /*LEX_R_DEFAULT    */ "default\0"
-        /*LEX_R_DELETE     */ "delete\0"
-        /*LEX_R_TYPEOF :   */ "typeof\0"
-        /*LEX_R_VOID :     */ "void\0"
-        /*LEX_R_DEBUGGER : */ "debugger\0"
-        /*LEX_R_CLASS :    */ "class\0"
-        /*LEX_R_EXTENDS :  */ "extends\0"
-        /*LEX_R_SUPER :  */   "super\0"
-        /*LEX_R_STATIC :   */ "static\0"
-        /*LEX_R_OF    :   */  "of\0"
-        ;
-    unsigned int p = 0;
-    int n = token-_LEX_OPERATOR_START;
-    while (n>0 && p<sizeof(tokenNames)) {
-      while (tokenNames[p] && p<sizeof(tokenNames)) p++;
-      p++; // skip the zero
-      n--; // next token
-    }
-    assert(n==0);
-    strcpy(str, &tokenNames[p]);
+    strcpy(str, jslReservedWordAsString(token));
     return;
   }
 
@@ -857,6 +861,7 @@ char *jslGetTokenValueAsString() {
     // pretokenised - so we'll work out the name from our token name list
     // this isn't fast, but won't be called very often
     jslTokenAsString(lex->tk, lex->token, sizeof(lex->token));
+    strcpy(lex->token, jslReservedWordAsString(lex->tk));
     lex->tokenl = (unsigned char)strlen(lex->token);
   }
   return lex->token;
@@ -869,6 +874,9 @@ int jslGetTokenLength() {
 JsVar *jslGetTokenValueAsVar() {
   if (lex->tokenValue) {
     return jsvLockAgain(lex->tokenValue);
+  } else if (lex->tk >= _LEX_R_LIST_START && lex->tk <= _LEX_R_LIST_END) {
+    // in pretokenised code, we must make this up
+    return jsvNewFromString(jslReservedWordAsString(lex->tk));
   } else {
     assert(lex->tokenl < JSLEX_MAX_TOKEN_LENGTH);
     lex->token[lex->tokenl]  = 0; // add final null