Error creating GPU graphics pipeline (SDL_gpu)

SDL Development
1

I’m trying to upload a triangle (3 vertices with x, y and z coords) to a GPU vertex buffer for rendering using SDL_gpu. I have the following code:

// Create the GPU pipeline
SDL_GPUGraphicsPipelineCreateInfo pipelineCreateInfo = {
    .target_info = {
        .num_color_targets = 1,
        .color_target_descriptions = (SDL_GPUColorTargetDescription[]){{
            .format = SDL_GetGPUSwapchainTextureFormat(device, window),
        }},
    },
    // This is set up to match the vertex shader layout!
    .vertex_input_state = (SDL_GPUVertexInputState){
        .num_vertex_buffers = 1,
        .vertex_buffer_descriptions = (SDL_GPUVertexBufferDescription[]){{
            .slot = 0,
            .input_rate = SDL_GPU_VERTEXINPUTRATE_VERTEX,
            .pitch = sizeof(Vec3_t),
        }},
        .num_vertex_attributes = 1,
        .vertex_attributes = (SDL_GPUVertexAttribute[]){{
            .buffer_slot = 0,
            .format = SDL_GPU_VERTEXELEMENTFORMAT_FLOAT3,
            .location = 0,
            .offset = 0,
        }}
    },
    .primitive_type = SDL_GPU_PRIMITIVETYPE_TRIANGLELIST,
    .vertex_shader = vertexShader,
    .fragment_shader = fragmentShader,
};

SDL_GPUGraphicsPipeline* pipeline = SDL_CreateGPUGraphicsPipeline(device, &pipelineCreateInfo);
if (pipeline == NULL) {
    SDL_Log("Unable to create graphics pipeline: %s", SDL_GetError());
    return 1;
}

Here are my (very simple) shaders in HLSL:

// vert.hlsl
struct VertexInput
{
    float3 position : POSITION;
};

struct VertexOutput
{
    float4 position : SV_Position;
};

VertexOutput MainVS(VertexInput input)
{
    VertexOutput output;
    output.position = float4(input.position, 1.0);
    return output;
}

// frag.hlsl
float4 MainPS() : SV_Target
{
    return float4(1.0f, 0.0f, 0.0f, 1.0f);
}

And I get the following error:

Unable to create graphics pipeline: Could not create graphics pipeline state! Error Code: The parameter is incorrect. (0x80070057)

Do you know what this error is about? Tried to search the source code for this error code, but found nothing. Also, I already checked the shaders and both are not NULL after creation. Same for device and window. I’m on version 3.1.6 of SDL.