diff --git a/backend/src/langs.ts b/backend/src/langs.ts
index 1494c67..a180e39 100644
--- a/backend/src/langs.ts
+++ b/backend/src/langs.ts
@@ -657,6 +657,25 @@ Put milk chocolate into the mixing bowl.
 Liquefy contents of the mixing bowl.
 Pour contents of the mixing bowl into the baking dish.
 Refrigerate for 1 hour.
+`,
+  },
+  cil: {
+    aliases: ["msil", "il", "ilasm"],
+    name: "CIL",
+    main: "main.il",
+    compile: "ilasm main.il",
+    run: "mono main.exe",
+    template: `.assembly main {}
+.class Main
+{
+  .method static void Main() cil managed
+  {
+    .entrypoint
+    ldstr "Hello, world!"
+    call void [mscorlib]System.Console::WriteLine(string)
+    ret
+  }
+}
 `,
   },
   clean: {
diff --git a/scripts/docker-install-phase3a.bash b/scripts/docker-install-phase3a.bash
index 28d5ec6..a1734e2 100755
--- a/scripts/docker-install-phase3a.bash
+++ b/scripts/docker-install-phase3a.bash
@@ -83,6 +83,9 @@ mono-mcs
 ${ceylon}
 openjdk-8-jdk-headless
 
+# CIL
+mono-devel
+
 # Clojure
 clojure