diff --git a/Project.toml b/Project.toml
index 99e7141ad..52c88b63d 100644
--- a/Project.toml
+++ b/Project.toml
@@ -70,7 +70,7 @@ MacroTools = "0.5"
 FileIO = "1"
 julia = "1.4"
 GlobalSensitivityAnalysis = "1.0"
-DataFrames = "0.19.1, 0.20, 0.21"
+DataFrames = "0.19.1, 0.20, 0.21, 0.22"
 FilePaths = "0.8"
 
 [targets]
diff --git a/src/explorer/buildspecs.jl b/src/explorer/buildspecs.jl
index eb5df501b..545c43d13 100644
--- a/src/explorer/buildspecs.jl
+++ b/src/explorer/buildspecs.jl
@@ -1089,10 +1089,11 @@ function trumpet_df_reduce(df, plottype::Symbol)
         i != col_index && push!(groupby_keys,  names(df)[i])
     end
 
-    df_new = by(df, groupby_keys, value = col => minimum)
-    append!(df_new, by(df, groupby_keys, value = col => maximum))
-    append!(df_new, by(df, groupby_keys, value = col => mean))
-    rename!(df_new, :value => col)
+    gd = DataFrames.groupby(df, groupby_keys)
+
+    df_new = rename!(combine(gd, col => maximum), Symbol(col, :_maximum) => col)
+    append!(df_new, rename!(combine(gd, col => minimum), Symbol(col, :_minimum) => col))
+    append!(df_new, rename!(combine(gd, col => mean), Symbol(col, :_mean) => col))
 
     if plottype == :trumpet
         reorder_cols = [groupby_keys[1], col, groupby_keys[2:end]...]
diff --git a/src/mcs/montecarlo.jl b/src/mcs/montecarlo.jl
index 1803a468e..a61b03eb3 100644
--- a/src/mcs/montecarlo.jl
+++ b/src/mcs/montecarlo.jl
@@ -64,13 +64,13 @@ function _store_param_results(m::AbstractModel, datum_key::Tuple{Symbol, Symbol}
         if haskey(results, datum_key)
             results_df = results[datum_key]
         else        
-            types = [typeof(value), Int]
+            cols = [[], []]
             names = [datum_name, :trialnum]
             if has_scen
-                push!(types, String)
+                push!(cols, [])
                 push!(names, :scen)
             end
-            results_df = DataFrame(types, names, 0)
+            results_df = DataFrame(cols, names)
             results[datum_key] = results_df
         end