diff --git a/godotenv.go b/godotenv.go
index c560be5..54eebf4 100644
--- a/godotenv.go
+++ b/godotenv.go
@@ -160,10 +160,10 @@ func Write(envMap map[string]string, filename string) error {
 }
 
 func isInt(s string) bool {
+    s = strings.TrimPrefix(s, "-")
+
     if len(s) == 0 {
 		return false
-	} else if s[0] == '-' {
-		s = s[1:]
 	}
 
 	for _, r := range s {
diff --git a/godotenv_test.go b/godotenv_test.go
index f489615..c79912b 100644
--- a/godotenv_test.go
+++ b/godotenv_test.go
@@ -493,6 +493,8 @@ func TestIsInt(t *testing.T) {
     checkAndCompare("12a3", false)
     checkAndCompare("abc", false)
     checkAndCompare("12 3", false)
+    checkAndCompare("-", false)
+    checkAndCompare(" ", false)
 
     // valid values
     checkAndCompare("-123", true)