diff --git a/proto2ros/proto2ros/output/interfaces.py b/proto2ros/proto2ros/output/interfaces.py
index 9585833..7f2b449 100644
--- a/proto2ros/proto2ros/output/interfaces.py
+++ b/proto2ros/proto2ros/output/interfaces.py
@@ -41,6 +41,16 @@ def dump_message_specification(message_spec: MessageSpecification) -> str:
                 any_type = Type(str(field.type).replace(BaseType.__str__(field.type), "proto2ros/Any"))
                 field = Field(any_type, field.name)
             line = str(field)
+            # ROS IDL does not allow a package to fully qualify its own type
+            # references: `proto2ros/Value` must be written as `Value` when
+            # the field appears in a message that itself belongs to `proto2ros`.
+            # rosidl's type-description generator fails with a KeyError when it
+            # encounters a self-qualified reference.  Strip the prefix here so
+            # the emitted .msg files conform to the rosidl convention used by
+            # every other ROS package.
+            self_pkg = message_spec.base_type.pkg_name
+            if field.type.pkg_name == self_pkg:
+                line = line.replace(f"{self_pkg}/", "", 1)
             if qualifiers:
                 line += "  # " + ", ".join(qualifiers)
             output.append(line)
diff --git a/proto2ros/proto2ros/output/test_interfaces.py b/proto2ros/proto2ros/output/test_interfaces.py
new file mode 100644
index 0000000..a9fa6f0
--- /dev/null
+++ b/proto2ros/proto2ros/output/test_interfaces.py
@@ -0,0 +1,44 @@
+# Copyright (c) 2024 Robotics and AI Institute LLC dba RAI Institute. All rights reserved.
+
+"""Unit tests for proto2ros.output.interfaces."""
+
+from rosidl_adapter.parser import Field, MessageSpecification, Type
+
+from proto2ros.output.interfaces import dump_message_specification
+
+
+def _make_spec(pkg: str, msg: str, fields: list) -> MessageSpecification:
+    return MessageSpecification(pkg, msg, fields, [])
+
+
+def test_dump_strips_self_package_qualifier() -> None:
+    """Same-package type references must not be fully qualified in .msg output.
+
+    rosidl's type-description generator fails with KeyError when a package
+    fully qualifies its own type references (e.g. ``proto2ros/Value`` inside
+    a ``proto2ros`` package message).  The emitted line must use the bare
+    type name instead.
+    """
+    fields = [Field(Type("proto2ros/Value[]"), "values")]
+    spec = _make_spec("proto2ros", "List", fields)
+    output = dump_message_specification(spec)
+    assert "proto2ros/Value" not in output, (
+        "self-package qualifier must be stripped from same-package field types"
+    )
+    assert "Value[] values" in output
+
+
+def test_dump_preserves_cross_package_qualifier() -> None:
+    """Cross-package type references must keep their fully qualified form."""
+    fields = [Field(Type("builtin_interfaces/Time"), "stamp")]
+    spec = _make_spec("my_msgs", "Header", fields)
+    output = dump_message_specification(spec)
+    assert "builtin_interfaces/Time stamp" in output
+
+
+def test_dump_preserves_primitive_fields() -> None:
+    """Messages with only primitive fields must be unaffected."""
+    spec = _make_spec("my_msgs", "Counts", [])
+    output = dump_message_specification(spec)
+    assert isinstance(output, str)
+