diff --git a/assets/basic.js b/assets/basic.js
index 80489de..e30313d 100644
--- a/assets/basic.js
+++ b/assets/basic.js
@@ -1995,12 +1995,11 @@ bF._executeSyntaxTree = function(lnum, syntaxTree, recDepth) {
             bF._recurseApplyAST(exprTree, (it) => {
                 if (it.astType == "lit") {
                     // check if parametre name is valid
-                    if (defunRenamingMap[it.astValue] === undefined) {
-                        throw lang.refError(lnum, it.astValue);
+                    // if the name is invalid, regard it as a global variable (i.e. do nothing)
+                    if (defunRenamingMap[it.astValue] !== undefined) {
+                        it.astType = "defun_args";
+                        it.astValue = defunRenamingMap[it.astValue];
                     }
-
-                    it.astType = "defun_args";
-                    it.astValue = defunRenamingMap[it.astValue];
                 }
                 // decrease the recursion counter while we're looping
                 it.astDepth -= 2;
diff --git a/assets/emit.bas b/assets/emit.bas
new file mode 100644
index 0000000..c8d29cb
--- /dev/null
+++ b/assets/emit.bas
@@ -0,0 +1,3 @@
+10 for k=0 to 1024
+20 emit(k mod 1024;)
+30 next
diff --git a/assets/facrec.bas b/assets/facrec.bas
new file mode 100644
index 0000000..5ca49fb
--- /dev/null
+++ b/assets/facrec.bas
@@ -0,0 +1,4 @@
+10 DEFUN FAC(N)=IF N==0 THEN 1 ELSE N*FAC(N-1)
+20 FOR K=1 TO 6
+30 PRINT FAC(K)
+40 NEXT