diff --git a/il65/examples/test.ill b/il65/examples/test.ill
index e1495c2e6..f4154154c 100644
--- a/il65/examples/test.ill
+++ b/il65/examples/test.ill
@@ -3,8 +3,14 @@
 
 %import c64lib
 
-~ main $c003  {
+~ not_main $d000 {
+    const float len1 =  111 ;len([1,2,3])
+    const float round1 =  111 ;len([1,2,3])
+    const float sin1 =  111 ;len([1,2,3])
+    float cos1 =  111 ;len([1,2,3])
+}
 
+~ main $c003  {
   const word len1 = len([1,2,3,wa1, wa2, ws1, all1])
   const word wa1 = ceil(abs(-999.22))
   const byte wa2 = abs(-99)
@@ -145,10 +151,6 @@ some_label_def:   A=44
 	%asmbinary "derp", 0, 200
 }
 
-%option enable_floats
-%option enable_floats
-%option enable_floats
-
 %import imported
 %import imported
 %import imported2
diff --git a/il65/src/il65/ast/AstIdentifiersChecker.kt b/il65/src/il65/ast/AstIdentifiersChecker.kt
index 9422ecb10..5385d2938 100644
--- a/il65/src/il65/ast/AstIdentifiersChecker.kt
+++ b/il65/src/il65/ast/AstIdentifiersChecker.kt
@@ -53,6 +53,10 @@ class AstIdentifiersChecker : IAstProcessor {
     }
 
     override fun process(decl: VarDecl): IStatement {
+        if(BuiltinFunctionNames.contains(decl.name))
+            // the builtin functions can't be redefined
+            checkResult.add(NameError("builtin function cannot be redefined", decl.position))
+
         val scopedName = decl.scopedname.joinToString(".")
         val existing = symbols[scopedName]
         if(existing!=null) {
diff --git a/il65/src/il65/compiler/Compiler.kt b/il65/src/il65/compiler/Compiler.kt
index ec8b86256..c34ed1004 100644
--- a/il65/src/il65/compiler/Compiler.kt
+++ b/il65/src/il65/compiler/Compiler.kt
@@ -30,7 +30,7 @@ fun Number.toHex(): String {
 }
 
 
-data class Mflpt5(val b0: Short, val b1: Short, val b2: Short, val b3: Short, val b4: Short){
+data class Mflpt5(val b0: Short, val b1: Short, val b2: Short, val b3: Short, val b4: Short) {
 
     companion object {
         val zero = Mflpt5(0, 0,0,0,0)