diff --git a/src/items.rs b/src/items.rs
index 55613ab1bb8..3b174190643 100644
--- a/src/items.rs
+++ b/src/items.rs
@@ -27,6 +27,7 @@ impl<'a> FmtVisitor<'a> {
                       explicit_self: Option<&ast::ExplicitSelf>,
                       generics: &ast::Generics,
                       unsafety: &ast::Unsafety,
+                      constness: &ast::Constness,
                       abi: &abi::Abi,
                       vis: ast::Visibility,
                       span_end: BytePos)
@@ -40,6 +41,7 @@ impl<'a> FmtVisitor<'a> {
                                               explicit_self,
                                               generics,
                                               unsafety,
+                                              constness,
                                               abi,
                                               vis,
                                               span_end,
@@ -74,6 +76,7 @@ impl<'a> FmtVisitor<'a> {
                                               Some(&sig.explicit_self),
                                               &sig.generics,
                                               &sig.unsafety,
+                                              &sig.constness,
                                               &sig.abi,
                                               ast::Visibility::Inherited,
                                               span_end,
@@ -92,6 +95,7 @@ impl<'a> FmtVisitor<'a> {
                        explicit_self: Option<&ast::ExplicitSelf>,
                        generics: &ast::Generics,
                        unsafety: &ast::Unsafety,
+                       constness: &ast::Constness,
                        abi: &abi::Abi,
                        vis: ast::Visibility,
                        span_end: BytePos,
@@ -111,6 +115,9 @@ impl<'a> FmtVisitor<'a> {
         if let &ast::Unsafety::Unsafe = unsafety {
             result.push_str("unsafe ");
         }
+        if let &ast::Constness::Const = constness {
+            result.push_str("const ");
+        }
         if *abi != abi::Rust {
             result.push_str("extern ");
             result.push_str(&abi.to_string());
diff --git a/src/visitor.rs b/src/visitor.rs
index 256c1e6e132..c15b3c34af0 100644
--- a/src/visitor.rs
+++ b/src/visitor.rs
@@ -98,13 +98,19 @@ impl<'a, 'v> visit::Visitor<'v> for FmtVisitor<'a> {
 
         let indent = self.block_indent;
         match fk {
-            visit::FkItemFn(ident, ref generics, ref unsafety, ref abi, vis) => {
+            visit::FkItemFn(ident,
+                            ref generics,
+                            ref unsafety,
+                            ref constness,
+                            ref abi,
+                            vis) => {
                 let new_fn = self.rewrite_fn(indent,
                                              ident,
                                              fd,
                                              None,
                                              generics,
                                              unsafety,
+                                             constness,
                                              abi,
                                              vis,
                                              b.span.lo);
@@ -117,6 +123,7 @@ impl<'a, 'v> visit::Visitor<'v> for FmtVisitor<'a> {
                                              Some(&sig.explicit_self),
                                              &sig.generics,
                                              &sig.unsafety,
+                                             &sig.constness,
                                              &sig.abi,
                                              vis.unwrap_or(ast::Visibility::Inherited),
                                              b.span.lo);
diff --git a/tests/idem/fn.rs b/tests/idem/fn.rs
index bbb9fa173d2..b78f6d9ffc3 100644
--- a/tests/idem/fn.rs
+++ b/tests/idem/fn.rs
@@ -58,6 +58,20 @@ pub fn render<'a,
     render_opts(g, w, &[])
 }
 
+const fn foo() {
+    x;
+}
+
+pub const fn foo() {
+    x;
+}
+
+impl Foo {
+    const fn foo() {
+        x;
+    }
+}
+
 fn main() {
     let _ = function(move || 5);
     let _ = move || 42;