diff --git a/codon/compiler/error.h b/codon/compiler/error.h
index b0671a9d..6b7be678 100644
--- a/codon/compiler/error.h
+++ b/codon/compiler/error.h
@@ -106,6 +106,7 @@ enum Error {
   SLICE_STEP_ZERO,
   OP_NO_MAGIC,
   INST_CALLABLE_STATIC,
+  CATCH_EXCEPTION_TYPE,
   TYPE_CANNOT_REALIZE_ATTR,
   TYPE_UNIFY,
   TYPE_FAILED,
@@ -426,6 +427,8 @@ template <class... TA> std::string Emsg(Error e, const TA &...args) {
     return fmt::format("unsupported operand type(s) for {}: '{}' and '{}'", args...);
   case Error::INST_CALLABLE_STATIC:
     return fmt::format("Callable cannot take static types");
+  case Error::CATCH_EXCEPTION_TYPE:
+    return fmt::format("'{}' does not inherit from BaseException", args...);
 
   case Error::TYPE_CANNOT_REALIZE_ATTR:
     return fmt::format("type of attribute '{}' of object '{}' cannot be inferred",
diff --git a/codon/parser/visitors/typecheck/error.cpp b/codon/parser/visitors/typecheck/error.cpp
index a26f3e0c..a946bef3 100644
--- a/codon/parser/visitors/typecheck/error.cpp
+++ b/codon/parser/visitors/typecheck/error.cpp
@@ -11,6 +11,7 @@ namespace codon::ast {
 
 using namespace types;
 using namespace matcher;
+using namespace error;
 
 /// Transform asserts.
 /// @example
@@ -119,6 +120,16 @@ void TypecheckVisitor::visit(TryStmt *stmt) {
     } else {
       // Handle all other exceptions
       c->exc = transformType(c->getException());
+
+      auto t = extractClassType(c->exc);
+      bool exceptionOK = false;
+      for (auto &p : getSuperTypes(t))
+        if (p->is("std.internal.types.error.BaseException.0")) {
+          exceptionOK = true;
+          break;
+        }
+      if (!exceptionOK)
+        E(Error::CATCH_EXCEPTION_TYPE, c->exc, t->toString());
       if (val)
         unify(val->getType(), extractType(c->getException()));
       ctx->blockLevel++;
diff --git a/jit/codon/__init__.py b/jit/codon/__init__.py
index 568e4bf9..e6ef34f9 100644
--- a/jit/codon/__init__.py
+++ b/jit/codon/__init__.py
@@ -3,3 +3,5 @@
 __all__ = ["jit", "convert", "JITError"]
 
 from .decorator import jit, convert, execute, JITError
+
+__codon__ = False
diff --git a/stdlib/internal/core.codon b/stdlib/internal/core.codon
index 443bbc2e..77bd5d6d 100644
--- a/stdlib/internal/core.codon
+++ b/stdlib/internal/core.codon
@@ -417,3 +417,5 @@ class ProxyFunc:
     data: Ptr[byte]
     T: type
     TR: type
+
+__codon__: Static[bool] = True
diff --git a/test/parser/typecheck/test_access.codon b/test/parser/typecheck/test_access.codon
index f6b0f2f9..5650f86f 100644
--- a/test/parser/typecheck/test_access.codon
+++ b/test/parser/typecheck/test_access.codon
@@ -569,3 +569,11 @@ def foo(x, y):
             return a
     return a
 print foo(5, (1, 2, 3))  #: 40
+
+#%% nontype_name,barebones
+class Foo:
+    def goo(self):
+        print(self.__name__)
+Foo().goo()
+#! error: 'Foo' object has no attribute '__name__'
+#! during the realization