diff --git a/src/main/scala/li/cil/oc/client/renderer/MonospaceFontRenderer.scala b/src/main/scala/li/cil/oc/client/renderer/MonospaceFontRenderer.scala
index b35c758ec..18f5eace4 100644
--- a/src/main/scala/li/cil/oc/client/renderer/MonospaceFontRenderer.scala
+++ b/src/main/scala/li/cil/oc/client/renderer/MonospaceFontRenderer.scala
@@ -12,7 +12,7 @@ import scala.io.Source
 
 object MonospaceFontRenderer {
   val (chars, fontWidth, fontHeight) = try {
-    val lines = Source.fromInputStream(Minecraft.getMinecraft.getResourceManager.getResource(new ResourceLocation(Settings.resourceDomain, "/textures/font/chars.txt")).getInputStream)("UTF-8").getLines
+    val lines = Source.fromInputStream(Minecraft.getMinecraft.getResourceManager.getResource(new ResourceLocation(Settings.resourceDomain, "/textures/font/chars.txt")).getInputStream)("UTF-8").getLines()
     val chars = lines.next()
     val (w, h) = if (lines.hasNext) {
       val size = lines.next().split(" ", 2)
diff --git a/src/main/scala/li/cil/oc/server/component/machine/luac/OSAPI.scala b/src/main/scala/li/cil/oc/server/component/machine/luac/OSAPI.scala
index 0d7c667dd..3bf8009aa 100644
--- a/src/main/scala/li/cil/oc/server/component/machine/luac/OSAPI.scala
+++ b/src/main/scala/li/cil/oc/server/component/machine/luac/OSAPI.scala
@@ -94,9 +94,10 @@ class OSAPI(owner: NativeLuaArchitecture) extends NativeLuaAPI(owner) {
         val mon = getField("month", -1)
         val year = getField("year", -1)
 
-        val time = GameTimeFormatter.mktime(year, mon, mday, hour, min, sec)
-        if (time == null) lua.pushNil()
-        else lua.pushNumber(time: Int)
+        GameTimeFormatter.mktime(year, mon, mday, hour, min, sec) match {
+          case Some(time) =>lua.pushNumber(time)
+          case _ => lua.pushNil()
+        }
       }
       1
     })
diff --git a/src/main/scala/li/cil/oc/server/component/machine/luaj/OSAPI.scala b/src/main/scala/li/cil/oc/server/component/machine/luaj/OSAPI.scala
index 899e92ca0..e7d4c5f99 100644
--- a/src/main/scala/li/cil/oc/server/component/machine/luaj/OSAPI.scala
+++ b/src/main/scala/li/cil/oc/server/component/machine/luaj/OSAPI.scala
@@ -74,9 +74,10 @@ class OSAPI(owner: LuaJLuaArchitecture) extends LuaJAPI(owner) {
         val mon = getField("month", -1)
         val year = getField("year", -1)
 
-        val time = GameTimeFormatter.mktime(year, mon, mday, hour, min, sec)
-        if (time == null) LuaValue.NIL
-        else LuaValue.valueOf(time: Int)
+        GameTimeFormatter.mktime(year, mon, mday, hour, min, sec) match {
+          case Some(time) => LuaValue.valueOf(time)
+          case _ => LuaValue.NIL
+        }
       }
     })
 
diff --git a/src/main/scala/li/cil/oc/util/GameTimeFormatter.scala b/src/main/scala/li/cil/oc/util/GameTimeFormatter.scala
index 54fdaca60..303ab62da 100644
--- a/src/main/scala/li/cil/oc/util/GameTimeFormatter.scala
+++ b/src/main/scala/li/cil/oc/util/GameTimeFormatter.scala
@@ -102,12 +102,12 @@ object GameTimeFormatter {
     result.toString()
   }
 
-  def mktime(year: Int, mon: Int, mday: Int, hour: Int, min: Int, sec: Int): Integer = {
-    if (year < 1970 || mon < 1 || mon > 12) return null
+  def mktime(year: Int, mon: Int, mday: Int, hour: Int, min: Int, sec: Int): Option[Int] = {
+    if (year < 1970 || mon < 1 || mon > 12) return None
     val monthLengths = monthLengthsForYear(year)
     val days = ((year - 1970) * 365.2425).ceil.toInt + (0 until mon - 1).foldLeft(0)((d, m) => d + monthLengths(m)) + mday - 1
     val secs = sec + (min + (hour - 1 + days * 24) * 60) * 60
-    if (secs < 0) null
-    else secs
+    if (secs < 0) None
+    else Option(secs)
   }
 }