diff --git a/backends/cxxrtl/runtime/cxxrtl/capi/cxxrtl_capi.h b/backends/cxxrtl/runtime/cxxrtl/capi/cxxrtl_capi.h
index e5c84bf65..c2a9d37e1 100644
--- a/backends/cxxrtl/runtime/cxxrtl/capi/cxxrtl_capi.h
+++ b/backends/cxxrtl/runtime/cxxrtl/capi/cxxrtl_capi.h
@@ -240,6 +240,11 @@ struct cxxrtl_object {
 	// through wires, the bits are double buffered. To avoid race conditions, user code should
 	// always read from `curr` and write to `next`. The `curr` pointer is always valid; for objects
 	// that cannot be modified, or cannot be modified in a race-free way, `next` is NULL.
+	//
+	// In case where `width == 0`, `curr` is a non-NULL pointer unique for the wire. That is,
+	// there is a 1-to-1 correspondence between simulation objects and `curr` pointers, regardless
+	// of whether they have storage or not. (Aliases' `curr` pointer equals that of some other
+	// simulated object.)
 	uint32_t *curr;
 	uint32_t *next;
 
diff --git a/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h b/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
index ee55011e8..8b7cf4da8 100644
--- a/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
+++ b/backends/cxxrtl/runtime/cxxrtl/cxxrtl.h
@@ -1176,7 +1176,7 @@ struct debug_item : ::cxxrtl_object {
 
 	template<size_t Bits>
 	debug_item(value<Bits> &item, size_t lsb_offset = 0, uint32_t flags_ = 0) {
-		static_assert(sizeof(item) == value<Bits>::chunks * sizeof(chunk_t),
+		static_assert(Bits == 0 || sizeof(item) == value<Bits>::chunks * sizeof(chunk_t),
 		              "value<Bits> is not compatible with C layout");
 		type    = VALUE;
 		flags   = flags_;
@@ -1192,7 +1192,7 @@ struct debug_item : ::cxxrtl_object {
 
 	template<size_t Bits>
 	debug_item(const value<Bits> &item, size_t lsb_offset = 0) {
-		static_assert(sizeof(item) == value<Bits>::chunks * sizeof(chunk_t),
+		static_assert(Bits == 0 || sizeof(item) == value<Bits>::chunks * sizeof(chunk_t),
 		              "value<Bits> is not compatible with C layout");
 		type    = VALUE;
 		flags   = DRIVEN_COMB;
@@ -1208,8 +1208,9 @@ struct debug_item : ::cxxrtl_object {
 
 	template<size_t Bits>
 	debug_item(wire<Bits> &item, size_t lsb_offset = 0, uint32_t flags_ = 0) {
-		static_assert(sizeof(item.curr) == value<Bits>::chunks * sizeof(chunk_t) &&
-		              sizeof(item.next) == value<Bits>::chunks * sizeof(chunk_t),
+		static_assert(Bits == 0 ||
+		              (sizeof(item.curr) == value<Bits>::chunks * sizeof(chunk_t) &&
+		               sizeof(item.next) == value<Bits>::chunks * sizeof(chunk_t)),
 		              "wire<Bits> is not compatible with C layout");
 		type    = WIRE;
 		flags   = flags_;
@@ -1225,7 +1226,7 @@ struct debug_item : ::cxxrtl_object {
 
 	template<size_t Width>
 	debug_item(memory<Width> &item, size_t zero_offset = 0) {
-		static_assert(sizeof(item.data[0]) == value<Width>::chunks * sizeof(chunk_t),
+		static_assert(Width == 0 || sizeof(item.data[0]) == value<Width>::chunks * sizeof(chunk_t),
 		              "memory<Width> is not compatible with C layout");
 		type    = MEMORY;
 		flags   = 0;
@@ -1241,7 +1242,7 @@ struct debug_item : ::cxxrtl_object {
 
 	template<size_t Bits>
 	debug_item(debug_alias, const value<Bits> &item, size_t lsb_offset = 0) {
-		static_assert(sizeof(item) == value<Bits>::chunks * sizeof(chunk_t),
+		static_assert(Bits == 0 || sizeof(item) == value<Bits>::chunks * sizeof(chunk_t),
 		              "value<Bits> is not compatible with C layout");
 		type    = ALIAS;
 		flags   = DRIVEN_COMB;
@@ -1257,8 +1258,9 @@ struct debug_item : ::cxxrtl_object {
 
 	template<size_t Bits>
 	debug_item(debug_alias, const wire<Bits> &item, size_t lsb_offset = 0) {
-		static_assert(sizeof(item.curr) == value<Bits>::chunks * sizeof(chunk_t) &&
-		              sizeof(item.next) == value<Bits>::chunks * sizeof(chunk_t),
+		static_assert(Bits == 0 ||
+		              (sizeof(item.curr) == value<Bits>::chunks * sizeof(chunk_t) &&
+		               sizeof(item.next) == value<Bits>::chunks * sizeof(chunk_t)),
 		              "wire<Bits> is not compatible with C layout");
 		type    = ALIAS;
 		flags   = DRIVEN_COMB;
@@ -1274,7 +1276,7 @@ struct debug_item : ::cxxrtl_object {
 
 	template<size_t Bits>
 	debug_item(debug_outline &group, const value<Bits> &item, size_t lsb_offset = 0) {
-		static_assert(sizeof(item) == value<Bits>::chunks * sizeof(chunk_t),
+		static_assert(Bits == 0 || sizeof(item) == value<Bits>::chunks * sizeof(chunk_t),
 		              "value<Bits> is not compatible with C layout");
 		type    = OUTLINE;
 		flags   = DRIVEN_COMB;