diff --git a/compiler/src/prog8/compiler/target/cpu6502/codegen/BuiltinFunctionsAsmGen.kt b/compiler/src/prog8/compiler/target/cpu6502/codegen/BuiltinFunctionsAsmGen.kt
index a9aebacd7..e54b1badc 100644
--- a/compiler/src/prog8/compiler/target/cpu6502/codegen/BuiltinFunctionsAsmGen.kt
+++ b/compiler/src/prog8/compiler/target/cpu6502/codegen/BuiltinFunctionsAsmGen.kt
@@ -65,7 +65,7 @@ internal class BuiltinFunctionsAsmGen(private val program: Program, private val
             "pokew" -> funcPokeW(fcall)
             "poke" -> throw AssemblyError("poke() should have been replaced by @()")
             "cmp" -> funcCmp(fcall)
-            else -> TODO("missing asmgen for builtin func ${func.name}")
+            else -> throw AssemblyError("missing asmgen for builtin func ${func.name}")
         }
     }