diff --git a/src/runtime/object.cpp b/src/runtime/object.cpp
index 866cc58093..763e52401a 100644
--- a/src/runtime/object.cpp
+++ b/src/runtime/object.cpp
@@ -139,7 +139,7 @@ void del(object * o) {
 
 #if 0
 static object * sarray_ensure_capacity(object * o, size_t extra) {
-    lean_assert(!is_shared(o));
+    lean_assert(!is_heap_obj(o) || !is_shared(o));
     size_t sz  = sarray_size(o);
     size_t cap = sarray_capacity(o);
     if (sz + extra > cap) {
@@ -161,7 +161,7 @@ static object * sarray_ensure_capacity(object * o, size_t extra) {
 static inline char * w_string_data(object * o) { lean_assert(is_string(o)); return reinterpret_cast<char *>(o) + sizeof(string_object); }
 
 static object * string_ensure_capacity(object * o, size_t extra) {
-    lean_assert(!is_shared(o));
+    lean_assert(!is_heap_obj(o) || !is_shared(o));
     size_t sz  = string_size(o);
     size_t cap = string_capacity(o);
     if (sz + extra > cap) {
@@ -195,7 +195,7 @@ object * mk_string(std::string const & s) {
 }
 
 object * string_push(object * s, unsigned c) {
-    lean_assert(!is_shared(s));
+    lean_assert(!is_heap_obj(s) || !is_shared(s));
     object * r = string_ensure_capacity(s, 5);
     size_t sz  = string_size(r);
     unsigned consumed = push_unicode_scalar(w_string_data(r) + sz - 1, c);
@@ -206,7 +206,7 @@ object * string_push(object * s, unsigned c) {
 }
 
 object * string_append(object * s1, object * s2) {
-    lean_assert(!is_shared(s1));
+    lean_assert(!is_heap_obj(s1) || !is_shared(s1));
     lean_assert(s1 != s2);
     size_t sz1 = string_size(s1);
     size_t sz2 = string_size(s2);
diff --git a/src/runtime/object.h b/src/runtime/object.h
index 2167bd69d4..68814a40ae 100644
--- a/src/runtime/object.h
+++ b/src/runtime/object.h
@@ -174,7 +174,6 @@ void del(object * o);
 
 static_assert(sizeof(atomic<rc_type>) == sizeof(rc_type),  "atomic<rc_type> and rc_type must have the same size"); // NOLINT
 
-
 inline void * alloc_heap_object(size_t sz) {
     void * r = malloc(sizeof(rc_type) + sz);
     *static_cast<rc_type *>(r) = 1;
@@ -268,7 +267,7 @@ inline T obj_data(object * o, size_t offset) {
 /* Set object data of type T */
 template<typename T>
 inline void obj_set_data(object * o, size_t offset, T v) {
-    lean_assert(!is_shared(o));
+    lean_assert(!is_heap_obj(o) || !is_shared(o));
     lean_assert(obj_header_size(o) <= offset);
     lean_assert(offset + sizeof(T) <= obj_byte_size(o));
     *(reinterpret_cast<T *>(reinterpret_cast<char *>(o) + offset)) = v;
@@ -439,7 +438,7 @@ template<typename T> inline T cnstr_scalar(b_obj_arg o, size_t offset) {
 }
 /* Update constructor field `i` */
 inline void cnstr_set_obj(u_obj_arg o, unsigned i, obj_arg v) {
-    lean_assert(!is_shared(o));
+    lean_assert(!is_heap_obj(o) || !is_shared(o));
     lean_assert(i < cnstr_num_objs(o));
     obj_set_data(o, sizeof(constructor_object) + sizeof(object*)*i, v); // NOLINT
 }
@@ -479,12 +478,12 @@ inline b_obj_res array_obj(b_obj_arg o, size_t i) {
 }
 inline void array_set_size(u_obj_arg o, size_t sz) {
     lean_assert(is_array(o));
-    lean_assert(!is_shared(o));
+    lean_assert(!is_heap_obj(o) || !is_shared(o));
     lean_assert(sz <= array_capacity(o));
     to_array(o)->m_size = sz;
 }
 inline void array_set_obj(u_obj_arg o, size_t i, obj_arg v) {
-    lean_assert(!is_shared(o));
+    lean_assert(!is_heap_obj(o) || !is_shared(o));
     lean_assert(i < array_size(o));
     obj_set_data(o, sizeof(array_object) + sizeof(object*)*i, v); // NOLINT
 }
@@ -502,7 +501,7 @@ template<typename T> void sarray_set_data(u_obj_arg o, size_t i, T v) {
 }
 inline void sarray_set_size(u_obj_arg o, size_t sz) {
     lean_assert(is_sarray(o));
-    lean_assert(!is_shared(o));
+    lean_assert(!is_heap_obj(o) || !is_shared(o));
     lean_assert(sz <= sarray_capacity(o));
     to_sarray(o)->m_size = sz;
 }
diff --git a/src/util/object_ref.h b/src/util/object_ref.h
index 37ed550d1d..dec8ddbd26 100644
--- a/src/util/object_ref.h
+++ b/src/util/object_ref.h
@@ -14,7 +14,7 @@ class object_ref {
     object * m_obj;
 public:
     object_ref():m_obj(box(0)) {}
-    explicit object_ref(object * o):m_obj(o) { lean_assert(is_scalar(o) || get_rc(o) > 0); }
+    explicit object_ref(object * o):m_obj(o) { lean_assert(is_scalar(o) || !is_heap_obj(o) || get_rc(o) > 0); }
     object_ref(object_ref const & s):m_obj(s.m_obj) { inc(m_obj); }
     object_ref(object_ref && s):m_obj(s.m_obj) { s.m_obj = box(0); }
     ~object_ref() { dec(m_obj); }