From cd1272609dc1d72afbb2dcf0978be5e31bf44aaf Mon Sep 17 00:00:00 2001
From: "John Barton (joho)" <jrbarton@gmail.com>
Date: Tue, 28 Mar 2017 11:39:40 +1100
Subject: [PATCH 1/2] Add failing test for override of empty var

---
 godotenv_test.go | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/godotenv_test.go b/godotenv_test.go
index 0a1aff6..a62bf87 100644
--- a/godotenv_test.go
+++ b/godotenv_test.go
@@ -100,10 +100,12 @@ func TestLoadDoesNotOverride(t *testing.T) {
 	// ensure NO overload
 	presets := map[string]string{
 		"OPTION_A": "do_not_override",
+		"OPTION_B": "",
 	}
 
 	expectedValues := map[string]string{
 		"OPTION_A": "do_not_override",
+		"OPTION_B": "",
 	}
 	loadEnvAndCompareValues(t, Load, envFileName, expectedValues, presets)
 }

From 034acc219052fab168a0b5c5c6537b3c9260e47c Mon Sep 17 00:00:00 2001
From: "John Barton (joho)" <jrbarton@gmail.com>
Date: Tue, 28 Mar 2017 11:54:56 +1100
Subject: [PATCH 2/2] Change check of existing env to respect empty (but set)
 vars.

---
 godotenv.go | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/godotenv.go b/godotenv.go
index 016acc1..0d9066c 100644
--- a/godotenv.go
+++ b/godotenv.go
@@ -119,8 +119,15 @@ func loadFile(filename string, overload bool) error {
 		return err
 	}
 
+	currentEnv := map[string]bool{}
+	rawEnv := os.Environ()
+	for _, rawEnvLine := range rawEnv {
+		key := strings.Split(rawEnvLine, "=")[0]
+		currentEnv[key] = true
+	}
+
 	for key, value := range envMap {
-		if os.Getenv(key) == "" || overload {
+		if !currentEnv[key] || overload {
 			os.Setenv(key, value)
 		}
 	}