set_source() not working with maplibre_compare_proxy()

[itendswells]

When I try to update the source of a layer using set_source() on a maplibre_compare_proxy() I get the following error:

Error on client while running Shiny app
"[object Object]" is not valid JSON

The same exact code works fine on a regular maplibre_proxy()

Here is a basic shiny app that demonstrates the issue:

library(shiny)
library(mapgl)
library(dplyr)
library(tidycensus)

tracts <- get_acs("tract", variables = "B01003_001", state = "17", county = "031", geometry = T)
block_groups <- get_acs("block group", variables = "B01003_001", state = "17", county = "031", geometry = T)

m <- maplibre() %>% 
  add_fill_layer(
    id = "data_layer",
    source = tracts,
    fill_color = "blue",
    fill_opacity = 0.5,
    fill_outline_color = "black"
  ) %>% 
  fit_bounds(tracts)

ui <- fluidPage(
  selectInput("left_data", "Left data: ", choices = c("tracts", "block groups")),
  selectInput("right_data", "Right data: ", choices = c("tracts", "block groups")),
  maplibreCompareOutput("compare_map"),
  maplibreOutput("reg_map")
)

server <- function(input, output, session) {

  output$compare_map <- renderMaplibreCompare({compare(m, m)})
  output$reg_map <- renderMaplibre({m})

  observeEvent(input$left_data, {
    if (input$left_data == "tracts") {
      source <- tracts
    } else {
      source <- block_groups
    }

    maplibre_compare_proxy("compare_map", map_side = "before") %>% 
      set_source(
        layer_id = "data_layer",
        source = source
      )

    maplibre_proxy("reg_map") %>% 
      set_source(
        layer_id = "data_layer",
        source = source
      )
  })

  observeEvent(input$right_data, {
    if (input$right_data == "tracts") {
      source <- tracts
    } else {
      source <- block_groups
    }

    maplibre_compare_proxy("compare_map", map_side = "after") %>% 
      set_source(
        layer_id = "data_layer",
        source = source
      )
  })

}

shinyApp(ui, server)