diff --git a/msgpack/_unpacker.pyx b/msgpack/_unpacker.pyx
index f758c0c4..e0463617 100644
--- a/msgpack/_unpacker.pyx
+++ b/msgpack/_unpacker.pyx
@@ -46,7 +46,7 @@ cdef extern from "unpack.h":
         Py_ssize_t count
 
     ctypedef int (*execute_fn)(unpack_context* ctx, const char* data,
-                               Py_ssize_t len, Py_ssize_t* off) except? -1
+                               Py_ssize_t len, Py_ssize_t* off) except -1
     execute_fn unpack_construct
     execute_fn unpack_skip
     execute_fn read_array_header
@@ -206,8 +206,6 @@ def unpackb(object packed, *, object object_hook=None, object list_hook=None,
         raise FormatError
     elif ret == -3:
         raise StackError
-    elif PyErr_Occurred():
-        raise
     else:
         raise ValueError("Unpack failed: error = %d" % (ret,))
 
@@ -502,8 +500,6 @@ cdef class Unpacker:
                     raise FormatError
                 elif ret == -3:
                     raise StackError
-                elif PyErr_Occurred():
-                    raise
                 else:
                     raise ValueError("Unpack failed: error = %d" % (ret,))
         finally:
diff --git a/msgpack/unpack.h b/msgpack/unpack.h
index 55cfdab9..eb4330ac 100644
--- a/msgpack/unpack.h
+++ b/msgpack/unpack.h
@@ -40,11 +40,6 @@ struct unpack_context;
 typedef struct unpack_context unpack_context;
 typedef int (*execute_fn)(unpack_context *ctx, const char* data, Py_ssize_t len, Py_ssize_t* off);
 
-static inline msgpack_unpack_object unpack_callback_root(unpack_user* u)
-{
-    return NULL;
-}
-
 static inline int unpack_callback_uint16(unpack_user* u, uint16_t d, msgpack_unpack_object* o)
 {
     PyObject *p = PyLong_FromLong((long)d);
diff --git a/msgpack/unpack_template.h b/msgpack/unpack_template.h
index ab5887ae..797a2f91 100644
--- a/msgpack/unpack_template.h
+++ b/msgpack/unpack_template.h
@@ -35,11 +35,6 @@ struct unpack_context {
     unsigned int cs;
     unsigned int trail;
     unsigned int top;
-    /*
-    unpack_stack* stack;
-    unsigned int stack_size;
-    unpack_stack embed_stack[MSGPACK_EMBED_STACK_SIZE];
-    */
     unpack_stack stack[MSGPACK_EMBED_STACK_SIZE];
 };
 
@@ -49,22 +44,9 @@ static inline void unpack_init(unpack_context* ctx)
     ctx->cs = CS_HEADER;
     ctx->trail = 0;
     ctx->top = 0;
-    /*
-    ctx->stack = ctx->embed_stack;
-    ctx->stack_size = MSGPACK_EMBED_STACK_SIZE;
-    */
-    ctx->stack[0].obj = unpack_callback_root(&ctx->user);
+    ctx->stack[0].obj = NULL;
 }
 
-/*
-static inline void unpack_destroy(unpack_context* ctx)
-{
-    if(ctx->stack_size != MSGPACK_EMBED_STACK_SIZE) {
-        free(ctx->stack);
-    }
-}
-*/
-
 static inline PyObject* unpack_data(unpack_context* ctx)
 {
     return (ctx)->stack[0].obj;
@@ -94,9 +76,6 @@ static inline int unpack_execute(bool construct, unpack_context* ctx, const char
     unsigned int cs = ctx->cs;
     unsigned int top = ctx->top;
     unpack_stack* stack = ctx->stack;
-    /*
-    unsigned int stack_size = ctx->stack_size;
-    */
     unpack_user* user = &ctx->user;
 
     PyObject* obj = NULL;
@@ -319,6 +298,7 @@ static inline int unpack_execute(bool construct, unpack_context* ctx, const char
                 start_container(_map, _msgpack_load32(uint32_t,n), CT_MAP_KEY);
 
             default:
+                PyErr_Format(PyExc_RuntimeError, "Invalid state: %d", cs);
                 goto _failed;
             }
         }
@@ -355,6 +335,7 @@ static inline int unpack_execute(bool construct, unpack_context* ctx, const char
         goto _header_again;
 
     default:
+        PyErr_Format(PyExc_RuntimeError, "Invalid container type: %u", c->ct);
         goto _failed;
     }