How to return a struct by value using JNR?

Question

I'm trying to work with the openh264 native library from Java code using JNR. The function I'm calling is defined in openh264's C header file to return a simple struct by value:

typedef struct  _tagVersion {
    unsigned int uMajor;
    unsigned int uMinor;
    unsigned int uRevision;
    unsigned int uReserved;
} OpenH264Version;

OpenH264Version WelsGetCodecVersion (void);

I wrote the following Java counterparts:

public class OpenH264Version extends Struct {

    public OpenH264Version(Runtime runtime) {
        super(runtime);
    }

    public Unsigned32 uMajor = new Unsigned32();
    public Unsigned32 uMinor = new Unsigned32();
    public Unsigned32 uRevision = new Unsigned32();
    public Unsigned32 uReserved = new Unsigned32();
}

public interface OpenH264 {
    public OpenH264Version WelsGetCodecVersion();
}

and finally trying it:

OpenH264 openH264 = LibraryLoader.create(OpenH264.class)
                    .load("openh264");
OpenH264Version version = openH264.WelsGetCodecVersion();

However, the returned version has wrong values (and they are different on each invocation).
The lib was x64 running on Windows 10 x64.
I could load the same lib with JNI+JavaCpp and the return values were correct.
What am I missing?