diff --git a/src/env.rs b/src/env.rs
index ce670695..4e35c2b8 100644
--- a/src/env.rs
+++ b/src/env.rs
@@ -71,14 +71,9 @@ impl Source for Environment {
         let mut m = HashMap::new();
         let uri: String = "the environment".into();
 
-        let separator = match self.separator {
-            Some(ref separator) => separator,
-            _ => "",
-        };
-
         // Define a prefix pattern to test and exclude from keys
         let prefix_pattern = match self.prefix {
-            Some(ref prefix) => Some(prefix.clone() + "_"),
+            Some(ref prefix) => Some((prefix.clone() + "_").to_lowercase()),
             _ => None,
         };
 
@@ -88,14 +83,11 @@ impl Source for Environment {
                 continue;
             }
 
-            let mut key = key.to_string();
+            let mut key = key.to_lowercase();
 
             // Check for prefix
             if let Some(ref prefix_pattern) = prefix_pattern {
-                if key
-                    .to_lowercase()
-                    .starts_with(&prefix_pattern.to_lowercase())
-                {
+                if key.starts_with(prefix_pattern) {
                     // Remove this prefix from the key
                     key = key[prefix_pattern.len()..].to_string();
                 } else {
@@ -104,13 +96,12 @@ impl Source for Environment {
                 }
             }
 
-            // If separator is given replace with `.`
-            if !separator.is_empty() {
+            if let Some(ref separator) = self.separator {
                 key = key.replace(separator, ".");
             }
 
             m.insert(
-                key.to_lowercase(),
+                key,
                 Value::new(Some(&uri), ValueKind::String(value)),
             );
         }