diff --git a/cliutils/config.nim b/cliutils/config.nim
index f11ce2a..e133c01 100644
--- a/cliutils/config.nim
+++ b/cliutils/config.nim
@@ -6,6 +6,12 @@ type
     docopt*: Table[string, Value]
     json*: JsonNode
 
+func keyNames(key: string): tuple[arg, env, json: string] =
+  result = (
+    "--" & key,
+    key.replace('-', '_').toUpper,
+    key.replace(re"(-\w)", proc (m: RegexMatch): string = ($m)[1..1].toUpper))
+
 template walkFieldDefs*(t: NimNode, body: untyped) =
   let tTypeImpl = t.getTypeImpl
 
@@ -52,9 +58,7 @@ proc findConfigFile*(name: string, otherLocations: seq[string] = @[]): string =
     raise newException(ValueError, "could not find configuration file")
 
 proc getVal*(cfg: CombinedConfig, key: string): string =
-  let argKey = "--" & key
-  let envKey = key.replace('-', '_').toUpper
-  let jsonKey = key.replace(re"(-\w)", proc (m: RegexMatch): string = ($m)[1..1].toUpper)
+  let (argKey, envKey, jsonKey) = keyNames(key)
 
   if cfg.docopt.contains(argKey) and cfg.docopt[argKey]: return $cfg.docopt[argKey]
   elif existsEnv(envKey): return getEnv(envKey)
@@ -75,9 +79,7 @@ proc getVal*(cfg: CombinedConfig, key, default: string): string =
   except: return default
 
 proc getJson*(cfg: CombinedConfig, key: string): JsonNode =
-  let argKey = "--" & key
-  let envKey = key.replace('-', '_').toUpper
-  let jsonKey = key.replace(re"(-\w)", proc (m: RegexMatch): string = ($m)[1..1].toUpper)
+  let (argKey, envKey, jsonKey) = keyNames(key)
 
   if cfg.docopt.contains(argKey) and cfg.docopt[argKey]: return parseJson($cfg.docopt[argKey])
   elif existsEnv(envKey): return parseJson(getEnv(envKey))
@@ -88,6 +90,14 @@ proc getJson*(cfg: CombinedConfig, key: string, default: JsonNode): JsonNode =
   try: return getJson(cfg, key)
   except: return default
 
+proc hasKey*(cfg: CombinedConfig, key: string): bool =
+  let (argKey, envKey, jsonKey) = keyNames(key)
+
+  return
+    (cfg.docopt.contains(argKey) and cfg.docopt[argKey]) or
+    existsEnv(envKey) or
+    cfg.json.hasKey(jsonKey)
+
 proc loadEnv*(): StringTableRef =
   result = newStringTable()