diff --git a/envconf.go b/envconf.go
index 882e879..3bb6abc 100644
--- a/envconf.go
+++ b/envconf.go
@@ -48,6 +48,9 @@ func NewConfig() *Config {
 			}
 
 			if unicode.IsLetter(getFirstRune(key)) {
+				if len(config.mapEnv[left]) == 0 {
+					config.mapEnv[left] = make(map[string]cEntry)
+				}
 				var entry cEntry
 				entry.value = splitted[1]
 				entry.dtype = TypeNone