diff --git a/betterproto/__init__.py b/betterproto/__init__.py
index 0e09de9..8f79270 100644
--- a/betterproto/__init__.py
+++ b/betterproto/__init__.py
@@ -733,7 +733,7 @@ class Message(ABC):
                 elif isinstance(v, list):
                     # Convert each item.
                     v = [i.to_dict(casing, include_default_values) for i in v]
-                    if v:
+                    if v or include_default_values:
                         output[cased_name] = v
                 else:
                     if v._serialized_on_wire or include_default_values: