diff --git a/envconf.go b/envconf.go
index d468015..6b5e8fb 100644
--- a/envconf.go
+++ b/envconf.go
@@ -76,6 +76,9 @@ func (c *Config) DefineDefault(key string, val string, dtype DataType) {
 }
 
 func (c *Config) Parse() {
+    if c.parsed {
+        return
+    }
     c.parsed = true
     for k,v := range c.env {
         if v.empty {