diff --git a/py/mpqstrraw.h b/py/mpqstrraw.h
index 6674a2c398..328cb73fac 100644
--- a/py/mpqstrraw.h
+++ b/py/mpqstrraw.h
@@ -32,6 +32,7 @@ Q(OSError)
 Q(SyntaxError)
 Q(TypeError)
 Q(ValueError)
+Q(OverflowError)
 
 Q(abs)
 Q(all)
diff --git a/py/obj.c b/py/obj.c
index bf7013ae41..c6e665376a 100644
--- a/py/obj.c
+++ b/py/obj.c
@@ -155,6 +155,8 @@ machine_int_t mp_obj_get_int(mp_obj_t arg) {
         return 1;
     } else if (MP_OBJ_IS_SMALL_INT(arg)) {
         return MP_OBJ_SMALL_INT_VALUE(arg);
+    } else if (MP_OBJ_IS_TYPE(arg, &int_type)) {
+        return mp_obj_int_get_checked(arg);
 #if MICROPY_ENABLE_FLOAT
     } else if (MP_OBJ_IS_TYPE(arg, &float_type)) {
         // TODO work out if this should be floor, ceil or trunc
diff --git a/py/obj.h b/py/obj.h
index 5ca0e01f68..af8a886e3f 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -261,6 +261,10 @@ void mp_obj_cell_set(mp_obj_t self_in, mp_obj_t obj);
 
 // int
 extern const mp_obj_type_t int_type;
+// For long int, returns value truncated to machine_int_t
+machine_int_t mp_obj_int_get(mp_obj_t self_in);
+// Will rains exception if value doesn't fit into machine_int_t
+machine_int_t mp_obj_int_get_checked(mp_obj_t self_in);
 
 // exception
 extern const mp_obj_type_t exception_type;
diff --git a/py/objint.c b/py/objint.c
index 477b8aa52b..49341d38a2 100644
--- a/py/objint.c
+++ b/py/objint.c
@@ -58,7 +58,7 @@ mp_obj_t int_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
 
 // This is called only with strings whose value doesn't fit in SMALL_INT
 mp_obj_t mp_obj_new_int_from_long_str(const char *s) {
-    assert(0);
+    nlr_jump(mp_obj_new_exception_msg(MP_QSTR_OverflowError, "long int not supported in this build"));
     return mp_const_none;
 }
 
@@ -68,8 +68,7 @@ mp_obj_t mp_obj_new_int_from_uint(machine_uint_t value) {
     if ((value & (WORD_MSBIT_HIGH | (WORD_MSBIT_HIGH >> 1))) == 0) {
         return MP_OBJ_NEW_SMALL_INT(value);
     }
-    // TODO: Raise exception
-    assert(0);
+    nlr_jump(mp_obj_new_exception_msg(MP_QSTR_OverflowError, "small int overflow"));
     return mp_const_none;
 }
 
@@ -77,8 +76,16 @@ mp_obj_t mp_obj_new_int(machine_int_t value) {
     if (MP_OBJ_FITS_SMALL_INT(value)) {
         return MP_OBJ_NEW_SMALL_INT(value);
     }
-    // TODO: Raise exception
-    assert(0);
+    nlr_jump(mp_obj_new_exception_msg(MP_QSTR_OverflowError, "small int overflow"));
     return mp_const_none;
 }
+
+machine_int_t mp_obj_int_get(mp_obj_t self_in) {
+    return MP_OBJ_SMALL_INT_VALUE(self_in);
+}
+
+machine_int_t mp_obj_int_get_checked(mp_obj_t self_in) {
+    return MP_OBJ_SMALL_INT_VALUE(self_in);
+}
+
 #endif
diff --git a/py/objint_longlong.c b/py/objint_longlong.c
index c940ce1ac3..24d693761e 100644
--- a/py/objint_longlong.c
+++ b/py/objint_longlong.c
@@ -120,9 +120,17 @@ mp_obj_t mp_obj_new_int_from_long_str(const char *s) {
     return o;
 }
 
-machine_int_t mp_obj_int_get_int(mp_obj_t self_in) {
+machine_int_t mp_obj_int_get(mp_obj_t self_in) {
+    if (MP_OBJ_IS_SMALL_INT(self_in)) {
+        return MP_OBJ_SMALL_INT_VALUE(self_in);
+    }
     mp_obj_int_t *self = self_in;
     return self->val;
 }
 
+machine_int_t mp_obj_int_get_checked(mp_obj_t self_in) {
+    // TODO: Check overflow
+    return mp_obj_int_get(self_in);
+}
+
 #endif
diff --git a/py/runtime.c b/py/runtime.c
index aa1b83a67f..89dbe7ab6a 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -89,6 +89,9 @@ void rt_init(void) {
     mp_map_add_qstr(&map_builtins, MP_QSTR_TypeError, mp_obj_new_exception(MP_QSTR_TypeError));
     mp_map_add_qstr(&map_builtins, MP_QSTR_SyntaxError, mp_obj_new_exception(MP_QSTR_SyntaxError));
     mp_map_add_qstr(&map_builtins, MP_QSTR_ValueError, mp_obj_new_exception(MP_QSTR_ValueError));
+    // Somehow CPython managed to have OverflowError not inherit from ValueError ;-/
+    // TODO: For MICROPY_CPYTHON_COMPAT==0 use ValueError to avoid exc proliferation
+    mp_map_add_qstr(&map_builtins, MP_QSTR_OverflowError, mp_obj_new_exception(MP_QSTR_OverflowError));
     mp_map_add_qstr(&map_builtins, MP_QSTR_OSError, mp_obj_new_exception(MP_QSTR_OSError));
     mp_map_add_qstr(&map_builtins, MP_QSTR_AssertionError, mp_obj_new_exception(MP_QSTR_AssertionError));