diff --git a/.travis.yml b/.travis.yml
index 804c96c..2e02b46 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,8 +3,7 @@ os:
     - linux
     - osx
 julia:
-    - 0.4
-    - 0.5
+    - 0.6
     - nightly
 notifications:
     email: false
diff --git a/REQUIRE b/REQUIRE
index 959f8ca..764c69c 100644
--- a/REQUIRE
+++ b/REQUIRE
@@ -1,2 +1,2 @@
-julia 0.4
+julia 0.6
 Compat 0.8.0
diff --git a/src/LaTeXStrings.jl b/src/LaTeXStrings.jl
index b5e54dd..7cac008 100644
--- a/src/LaTeXStrings.jl
+++ b/src/LaTeXStrings.jl
@@ -12,7 +12,7 @@ import Compat.String
 # \\beta\$".  To simplify this, we add a new string type with a macro
 # constructor, so that one can simply do L"$\alpha + \beta$".
 
-immutable LaTeXString <: AbstractString
+struct LaTeXString <: AbstractString
     s::String
 end