Weird lang warning

gistfile1.txt

[23:42:15] [Server thread/WARN] [ne.mi.fm.se.LanguageHook/]: Skipped language file: farmers delight:lang/en_us.json
net.minecraft.util.ResourceLocationException: Non [a-z0-9_.-] character in namespace of location: farmers delight:lang/en_us.json
at net.minecraft.util.ResourceLocation.<init>(SourceFile:35) ~[?:?] {re:classloading}
at net.minecraft.util.ResourceLocation.<init>(SourceFile:47) ~[?:?] {re:classloading}
at net.minecraftforge.fml.server.LanguageHook.lambda$loadLanguage$2(LanguageHook.java:85) ~[?:?] {re:classloading}
at java.lang.Iterable.forEach(Iterable.java:75) ~[?:1.8.0_171] {}
at net.minecraftforge.fml.server.LanguageHook.loadLanguage(LanguageHook.java:83) ~[?:?] {re:classloading}
at net.minecraftforge.fml.server.LanguageHook.loadLanguagesOnServer(LanguageHook.java:109) ~[?:?] {re:classloading}
at net.minecraftforge.fml.server.ServerLifecycleHooks.lambda$null$1(ServerLifecycleHooks.java:94) ~[?:?] {re:classloading}
at net.minecraftforge.fml.DistExecutor.unsafeRunWhenOn(DistExecutor.java:125) [?:?] {re:classloading}
at net.minecraftforge.fml.DistExecutor.runWhenOn(DistExecutor.java:109) [?:?] {re:classloading}
at net.minecraftforge.fml.server.ServerLifecycleHooks.handleServerStarting(ServerLifecycleHooks.java:94) [?:?] {re:classloading}
at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:243) [?:?] {re:classloading,pl:accesstransformer:B}
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:613) [?:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_171] {}