1 files changed, 1 insertions, 1 deletions
diff --git a/src/env.rs b/src/env.rs
index dd237db..5c80bad 100644
--- a/src/env.rs
+++ b/src/env.rs
@@ -21,7 +21,7 @@ impl Environment {
 }
 
 impl source::SourceBuilder for Environment {
-    fn build(&self) -> Result<Box<source::Source>, Box<Error>> {
+    fn build(&self) -> Result<Box<source::Source + Send + Sync>, Box<Error>> {
         Ok(Box::new(self.clone()))
     }
 }