diff --git a/src/crop/almass.jl b/src/crop/almass.jl
index 14fec6d4405a9ae1e52dabf4cc88a3c0de83f8d4..d28238cea04c9a7ba9ffd1e6953acc7801401a79 100644
--- a/src/crop/almass.jl
+++ b/src/crop/almass.jl
@@ -93,6 +93,7 @@ struct CropType
     # not here. Also, we need to harmonise crops across the crop growth models.
     name::String
     group::String
+    is_c4_plant::Bool  # false means it is a C3 plant
     minsowdate::Union{Missing,AnnualDate}
     maxsowdate::Union{Missing,AnnualDate}
     minharvestdate::Union{Missing,AnnualDate}
@@ -250,8 +251,12 @@ function readcropparameters(generalcropfile::String, growthfile::String)
         # TODO: set crop group temporarily until there is a column in
         # the csv file
         crop_group = "CROP_GROUP_NOT_SET"
-        croptypes[crop.name] = CropType(crop.name, crop_group, crop.minsowdate, crop.maxsowdate,
-                                        crop.minharvestdate, crop.maxharvestdate,
+        # TODO: it would be better to save this in the parameter file
+        # (Note that this matches the current ALMaSS code though,
+        # which also only hardcodes maize as a C4 crop)
+        is_c4_plant = occursin("maize", lowercase(crop.name))
+        croptypes[crop.name] = CropType(crop.name, crop_group, is_c4_plant, crop.minsowdate,
+                                        crop.maxsowdate, crop.minharvestdate, crop.maxharvestdate,
                                         crop.mingrowthtemp, highnuts, lownuts)
     end
     croptypes
diff --git a/test/crop_tests.jl b/test/crop_tests.jl
index 9632b1d59549eea5decd4909982b54e16fce2eb4..852608516c3cc79b80a2abf746e8dc65429f7685 100644
--- a/test/crop_tests.jl
+++ b/test/crop_tests.jl
@@ -19,7 +19,7 @@ const TESTPARAM_SIMPLECROP = joinpath(pkgdir(Persefone), "test", "test_parameter
 end
 
 @testset "Submodule ALMaSS" begin
-    ct = Ps.ALMaSS.CropType("olive tree", "no_crop_group",
+    ct = Ps.ALMaSS.CropType("olive tree", "no_crop_group", false,
                             missing, missing, missing, missing, missing, missing, missing)
     id = 0
     pixels = [(0, 0)]