diff --git a/nac3artiq/language.py b/nac3artiq/language.py
index 77d79b2a..101bbcf4 100644
--- a/nac3artiq/language.py
+++ b/nac3artiq/language.py
@@ -1,4 +1,4 @@
-from inspect import isclass
+from inspect import isclass, getmodule
 from functools import wraps
 
 import nac3artiq
@@ -8,28 +8,28 @@ __all__ = ["extern", "kernel"]
 
 
 nac3 = nac3artiq.NAC3()
-allow_object_registration = True
+allow_module_registration = True
 
 
 def extern(function):
-    assert allow_object_registration
-    nac3.register_object(function)
+    assert allow_module_registration
+    nac3.register_module(getmodule(function))
     return function
 
 
-def kernel(function_or_class):
-    global allow_object_registration
+def kernel(class_or_function):
+    global allow_module_registration
 
-    if isclass(function_or_class):
-        assert allow_object_registration
-        nac3.register_object(function_or_class)
-        return function_or_class
+    assert allow_module_registration
+    nac3.register_module(getmodule(class_or_function))
+    if isclass(class_or_function):
+        return class_or_function
     else:
-        @wraps(function_or_class)
+        @wraps(class_or_function)
         def run_on_core(self, *args, **kwargs):
-            global allow_object_registration
-            if allow_object_registration:
+            global allow_module_registration
+            if allow_module_registration:
                 nac3.analyze()
-                allow_object_registration = False
-            nac3.compile_method(self.__class__.__name__, function_or_class.__name__)
+                allow_module_registration = False
+            nac3.compile_method(self.__class__.__name__, class_or_function.__name__)
         return run_on_core
diff --git a/nac3artiq/src/lib.rs b/nac3artiq/src/lib.rs
index 4dec48ad..a391dc6e 100644
--- a/nac3artiq/src/lib.rs
+++ b/nac3artiq/src/lib.rs
@@ -1,3 +1,4 @@
+use std::fs;
 use std::collections::{HashMap, HashSet};
 use std::sync::Arc;
 use std::path::Path;
@@ -5,7 +6,7 @@ use std::process::Command;
 
 use pyo3::prelude::*;
 use pyo3::exceptions;
-use rustpython_parser::parser;
+use rustpython_parser::{ast, parser};
 use inkwell::{
     passes::{PassManager, PassManagerBuilder},
     targets::*,
@@ -31,7 +32,8 @@ struct Nac3 {
     internal_resolver: Arc<ResolverInternal>,
     resolver: Arc<Box<dyn SymbolResolver + Send + Sync>>,
     composer: TopLevelComposer,
-    top_level: Option<Arc<TopLevelContext>>
+    top_level: Option<Arc<TopLevelContext>>,
+    registered_module_ids: HashSet<u64>
 }
 
 #[pymethods]
@@ -63,33 +65,57 @@ impl Nac3 {
             internal_resolver,
             resolver,
             composer,
-            top_level: None
+            top_level: None,
+            registered_module_ids: HashSet::new()
         }
     }
 
-    fn register_object(&mut self, obj: PyObject) -> PyResult<()> {
-        Python::with_gil(|py| -> PyResult<()> {
+    fn register_module(&mut self, obj: PyObject) -> PyResult<()> {
+        let module_info = Python::with_gil(|py| -> PyResult<Option<(String, String)>> {
             let obj: &PyAny = obj.extract(py)?;
+            let builtins = PyModule::import(py, "builtins")?;
+            let id = builtins.getattr("id")?.call1((obj, ))?.extract()?;
+            if self.registered_module_ids.insert(id) {
+                Ok(Some((obj.getattr("__name__")?.extract()?, obj.getattr("__file__")?.extract()?)))
+            } else {
+                Ok(None)
+            }
+        })?;
 
-            let source = PyModule::import(py, "inspect")?.getattr("getsource")?.call1((obj, ))?.extract()?;
-            let parser_result = parser::parse_program(source).map_err(|e|
+        if let Some((module_name, source_file)) = module_info {
+            let source = fs::read_to_string(source_file).map_err(|e|
+                exceptions::PyIOError::new_err(format!("failed to read input file: {}", e)))?;
+            let parser_result = parser::parse_program(&source).map_err(|e|
                 exceptions::PySyntaxError::new_err(format!("failed to parse host object source: {}", e)))?;
 
             for stmt in parser_result.into_iter() {
-                let (name, def_id, ty) = self.composer.register_top_level(
-                    stmt,
-                    Some(self.resolver.clone()),
-                    "__main__".into(),
-                ).unwrap();
+                let include = match &stmt.node {
+                    ast::StmtKind::ClassDef { decorator_list, .. } => {
+                        decorator_list.iter().any(|decorator| if let ast::ExprKind::Name { id, .. } = decorator.node
+                            { id.to_string() == "kernel" || id.to_string() == "portable" } else { false })
+                    },
+                    ast::StmtKind::FunctionDef { decorator_list, .. } => {
+                        decorator_list.iter().any(|decorator| if let ast::ExprKind::Name { id, .. } = decorator.node
+                            { id.to_string() == "extern" || id.to_string() == "portable" } else { false })
+                    },
+                    _ => false
+                };
 
-                self.internal_resolver.add_id_def(name.clone(), def_id);
-                if let Some(ty) = ty {
-                    self.internal_resolver.add_id_type(name, ty);
+                if include {
+                    let (name, def_id, ty) = self.composer.register_top_level(
+                        stmt,
+                        Some(self.resolver.clone()),
+                        module_name.clone(),
+                    ).unwrap();
+
+                    self.internal_resolver.add_id_def(name.clone(), def_id);
+                    if let Some(ty) = ty {
+                        self.internal_resolver.add_id_type(name, ty);
+                    }
                 }
             }
-
-            Ok(())
-        })
+        }
+        Ok(())
     }
 
     fn analyze(&mut self) -> PyResult<()> {