diff --git a/backends/cxxrtl/runtime/cxxrtl/cxxrtl_vcd.h b/backends/cxxrtl/runtime/cxxrtl/cxxrtl_vcd.h
index e4c9a67702c..e8be7002814 100644
--- a/backends/cxxrtl/runtime/cxxrtl/cxxrtl_vcd.h
+++ b/backends/cxxrtl/runtime/cxxrtl/cxxrtl_vcd.h
@@ -127,6 +127,8 @@ class vcd_writer {
 			bool bit_curr = var.curr[bit / (8 * sizeof(chunk_t))] & (1 << (bit % (8 * sizeof(chunk_t))));
 			buffer += (bit_curr ? '1' : '0');
 		}
+		if (var.width == 0)
+			buffer += '0';
 		buffer += ' ';
 		emit_ident(var.ident);
 		buffer += '\n';