diff --git a/Makefile b/Makefile
index 03e77ed..fb72724 100644
--- a/Makefile
+++ b/Makefile
@@ -4,10 +4,10 @@ GENERATED := $(patsubst %Generator.cs,%Generated.cs,$(GENERATORS))
 
 .PHONY: run
 run: main.exe
-	mono main.exe
+	MONO_PATH=/usr/lib/mono/4.5/:/usr/lib/mono/4.5/Facades/ mono main.exe
 
 main.exe: $(sort $(CS) $(GENERATED))
-	mcs -out:$@ /reference:/usr/lib/mono/fsharp/FSharp.Core.dll $^
+	mcs -out:$@ -sdk:45 /reference:/usr/lib/mono/fsharp/FSharp.Core.dll /reference:/usr/lib/mono/4.5/System.Collections.Immutable.dll /reference:/usr/lib/mono/4.5/Facades/netstandard.dll $^
 
 %Generated.cs: .%Generator.exe
 	mono $<