free_y_axis does not work in Gadfly (Julia)

Question

I'm trying to make a facet barplot with independent y axes in Gadfly. For that I'm using free_y_axis = true, which does work. However, when I add the color aesthetic (color=:product), free_y_axis does not seem to work anymore. Any ideas?

The code for the plots is:

using Gadfly
using DataFrames

plot(flow, ygroup=:rawmat_type, x=:period, y=:quantity, color=:product, 
    Geom.subplot_grid(Geom.bar(position=:stack), free_y_axis=true), 
    Theme(background_color="white", bar_spacing=2mm, key_title_font_size=9pt), 
    Scale.y_continuous(format=:plain))

And the flow data frame is:

 Row │ product    rawmat    type  period   quantity   rawmat_type       
─────┼──────────────────────────────────────────────────────────────
   1 │ lemon_pie  cookies  cheap         1   10000.0  cookies_cheap
   2 │ lemon_pie  cookies  cheap         2   10000.0  cookies_cheap
   3 │ lemon_pie  cookies  cheap         3   10000.0  cookies_cheap
   4 │ lemon_pie  cookies  cheap         4   10000.0  cookies_cheap
   5 │ lemon_pie  cookies  cheap         5   10000.0  cookies_cheap
   6 │ brownie    sugar    cane          1     100.0  sugar_cane
   7 │ brownie    sugar    cane          2     100.0  sugar_cane
   8 │ brownie    sugar    cane          3     100.0  sugar_cane
   9 │ brownie    sugar    cane          4     100.0  sugar_cane
  10 │ brownie    sugar    cane          5     100.0  sugar_cane
  11 │ lemon_pie  lemon    cheap         1    1000.0  lemon_cheap
  12 │ lemon_pie  lemon    cheap         2    1000.0  lemon_cheap
  13 │ lemon_pie  lemon    cheap         3    1000.0  lemon_cheap
  14 │ lemon_pie  lemon    cheap         4    1000.0  lemon_cheap
  15 │ lemon_pie  lemon    cheap         5    1000.0  lemon_cheap
  16 │ brownie    cacao    bitter        1     250.0  cacao_bitter
  17 │ brownie    cacao    bitter        2     250.0  cacao_bitter
  18 │ brownie    cacao    bitter        3     250.0  cacao_bitter
  19 │ brownie    cacao    bitter        4     250.0  cacao_bitter
  20 │ brownie    cacao    bitter        5     250.0  cacao_bitter
  21 │ lemon_pie  lemon    premium       1     500.0  lemon_premium
  22 │ lemon_pie  lemon    premium       2     500.0  lemon_premium
  23 │ lemon_pie  lemon    premium       3     500.0  lemon_premium
  24 │ lemon_pie  lemon    premium       4     500.0  lemon_premium
  25 │ lemon_pie  lemon    premium       5     500.0  lemon_premium

I attach the plot that I get and in which I'd like to free the y-axes while still using the color aesthetic for the product variable. bakery plot

Thanks!