Using multiple uniform blocks in OpenGL

I'm using OpenGL with JOGL and want to use two unfirorm blocks in my vertex and pixel shaders. The following GLSL-Code shows the definitions:-

uniform perObject
{
    Material uMaterial;
    mat4 uWorld;
    mat4 uWorldViewProj;
};

uniform perFrame
{
    vec3 uEyePosW;
    PointLight uPointLight;
};

My Java code looks like this:

perObjectIndex = gl.glGetUniformBlockIndex(shaderProgram, "perObject");
gl.glUniformBlockBinding(shaderProgram, perObjectIndex, 0);

perFrameIndex = gl.glGetUniformBlockIndex(shaderProgram, "perFrame");
gl.glUniformBlockBinding(shaderProgram, perFrameIndex, 1);

gl.glGenBuffers(2, uniformBufferHandles, 0);
perObjectBufferHandle = uniformBufferHandles[0];    
perFrameBufferHandle = uniformBufferHandles[1]; 

gl.glBindBuffer(GL3.GL_UNIFORM_BUFFER, perObjectBufferHandle);
gl.glBufferData(GL3.GL_UNIFORM_BUFFER, perObjectBuffer.capacity(), perObjectBuffer, GL3.GL_DYNAMIC_DRAW);
gl.glBindBufferBase(GL3.GL_UNIFORM_BUFFER, 0, perObjectBufferHandle);

gl.glBindBuffer(GL3.GL_UNIFORM_BUFFER, perFrameBufferHandle);
gl.glBufferData(GL3.GL_UNIFORM_BUFFER, perFrameBuffer.capacity(), perFrameBuffer, GL3.GL_DYNAMIC_DRAW);
gl.glBindBufferBase(GL3.GL_UNIFORM_BUFFER, 1, perFrameBufferHandle);

However, if I remove the code for the perFrameBlock, everything seems to work very fine. In a draw method I update the data in the following way:

gl.glBindBuffer(GL3.GL_UNIFORM_BUFFER, perObjectBufferHandle);
gl.glBufferSubData(GL3.GL_UNIFORM_BUFFER, 0, perObjectBuffer.capacity(), perObjectBuffer);

All the data is properly transferred to the GPU. But if I want to use both uniform blocks, something strange seems to happen. Using glGetActiveUniformsiv with GL_UNIFORM_OFFSET it looks like the two blocks are merged in an alphabetic way depending on the variable names.

I thought I can deal with both blocks independently, provide one ByteBuffer for each block and transfer data to the corresponding block by invoking glBindBuffer and glBufferSubData.

How can I achieve my goal?