diff --git a/.travis.yml b/.travis.yml
index 218d7f9c..85769bd1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,6 +2,7 @@ language: rust
 
 rust:
     - stable
+    - 1.20.0
 
 sudo: false
 
diff --git a/src/write.rs b/src/write.rs
index ce3bae54..e46ac03f 100644
--- a/src/write.rs
+++ b/src/write.rs
@@ -19,6 +19,8 @@ use msdos_time::TmMsDosExt;
 use bzip2;
 #[cfg(feature = "bzip2")]
 use bzip2::write::BzEncoder;
+#[allow(unused_imports)] // Rust <1.23 compat
+use std::ascii::AsciiExt;
 
 enum GenericZipWriter<W: Write + io::Seek>
 {