diff --git a/src/libsyntax/ext/deriving/clone.rs b/src/libsyntax/ext/deriving/clone.rs
index 0d8fb471429..d99156bfa45 100644
--- a/src/libsyntax/ext/deriving/clone.rs
+++ b/src/libsyntax/ext/deriving/clone.rs
@@ -39,6 +39,7 @@ pub fn expand_deriving_clone(cx: &mut ExtCtxt,
                 args: Vec::new(),
                 ret_ty: Self_,
                 attributes: attrs,
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(|c, s, sub| {
                     cs_clone("Clone", c, s, sub)
                 })),
diff --git a/src/libsyntax/ext/deriving/cmp/eq.rs b/src/libsyntax/ext/deriving/cmp/eq.rs
index bd7c7d85a37..2a58ba2fc54 100644
--- a/src/libsyntax/ext/deriving/cmp/eq.rs
+++ b/src/libsyntax/ext/deriving/cmp/eq.rs
@@ -59,6 +59,7 @@ fn cs_total_eq_assert(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<
                 args: vec!(),
                 ret_ty: nil_ty(),
                 attributes: attrs,
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     cs_total_eq_assert(a, b, c)
                 }))
diff --git a/src/libsyntax/ext/deriving/cmp/ord.rs b/src/libsyntax/ext/deriving/cmp/ord.rs
index b4caf0ec26e..af36428437c 100644
--- a/src/libsyntax/ext/deriving/cmp/ord.rs
+++ b/src/libsyntax/ext/deriving/cmp/ord.rs
@@ -40,6 +40,7 @@ pub fn expand_deriving_ord(cx: &mut ExtCtxt,
                 args: vec!(borrowed_self()),
                 ret_ty: Literal(path_std!(cx, core::cmp::Ordering)),
                 attributes: attrs,
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     cs_cmp(a, b, c)
                 })),
diff --git a/src/libsyntax/ext/deriving/cmp/partial_eq.rs b/src/libsyntax/ext/deriving/cmp/partial_eq.rs
index 5d744334745..b330c1de180 100644
--- a/src/libsyntax/ext/deriving/cmp/partial_eq.rs
+++ b/src/libsyntax/ext/deriving/cmp/partial_eq.rs
@@ -71,6 +71,7 @@ macro_rules! md {
                 args: vec!(borrowed_self()),
                 ret_ty: Literal(path_local!(bool)),
                 attributes: attrs,
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     $f(a, b, c)
                 }))
diff --git a/src/libsyntax/ext/deriving/cmp/partial_ord.rs b/src/libsyntax/ext/deriving/cmp/partial_ord.rs
index 3ef73f6556e..557cce63346 100644
--- a/src/libsyntax/ext/deriving/cmp/partial_ord.rs
+++ b/src/libsyntax/ext/deriving/cmp/partial_ord.rs
@@ -37,6 +37,7 @@ macro_rules! md {
                 args: vec!(borrowed_self()),
                 ret_ty: Literal(path_local!(bool)),
                 attributes: attrs,
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(|cx, span, substr| {
                     cs_op($op, $equal, cx, span, substr)
                 }))
@@ -60,6 +61,7 @@ macro_rules! md {
         args: vec![borrowed_self()],
         ret_ty: ret_ty,
         attributes: attrs,
+        is_unsafe: false,
         combine_substructure: combine_substructure(Box::new(|cx, span, substr| {
             cs_partial_cmp(cx, span, substr)
         }))
diff --git a/src/libsyntax/ext/deriving/decodable.rs b/src/libsyntax/ext/deriving/decodable.rs
index 75c9bc42ea2..d21373c4a0b 100644
--- a/src/libsyntax/ext/deriving/decodable.rs
+++ b/src/libsyntax/ext/deriving/decodable.rs
@@ -79,6 +79,7 @@ fn expand_deriving_decodable_imp(cx: &mut ExtCtxt,
                     true
                 )),
                 attributes: Vec::new(),
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     decodable_substructure(a, b, c, krate)
                 })),
diff --git a/src/libsyntax/ext/deriving/default.rs b/src/libsyntax/ext/deriving/default.rs
index e9984c84e32..84b91a252a6 100644
--- a/src/libsyntax/ext/deriving/default.rs
+++ b/src/libsyntax/ext/deriving/default.rs
@@ -39,6 +39,7 @@ pub fn expand_deriving_default(cx: &mut ExtCtxt,
                 args: Vec::new(),
                 ret_ty: Self_,
                 attributes: attrs,
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     default_substructure(a, b, c)
                 }))
diff --git a/src/libsyntax/ext/deriving/encodable.rs b/src/libsyntax/ext/deriving/encodable.rs
index 4430c58700a..08037c0308d 100644
--- a/src/libsyntax/ext/deriving/encodable.rs
+++ b/src/libsyntax/ext/deriving/encodable.rs
@@ -155,6 +155,7 @@ fn expand_deriving_encodable_imp(cx: &mut ExtCtxt,
                     true
                 )),
                 attributes: Vec::new(),
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     encodable_substructure(a, b, c)
                 })),
diff --git a/src/libsyntax/ext/deriving/generic/mod.rs b/src/libsyntax/ext/deriving/generic/mod.rs
index 1525f1a822b..b9968ca9608 100644
--- a/src/libsyntax/ext/deriving/generic/mod.rs
+++ b/src/libsyntax/ext/deriving/generic/mod.rs
@@ -253,6 +253,9 @@ pub struct MethodDef<'a> {
 
     pub attributes: Vec<ast::Attribute>,
 
+    // Is it an `unsafe fn`?
+    pub is_unsafe: bool,
+
     pub combine_substructure: RefCell<CombineSubstructureFunc<'a>>,
 }
 
@@ -859,6 +862,12 @@ fn create_method(&self,
         let fn_decl = cx.fn_decl(args, ret_type);
         let body_block = cx.block_expr(body);
 
+        let unsafety = if self.is_unsafe {
+            ast::Unsafety::Unsafe
+        } else {
+            ast::Unsafety::Normal
+        };
+
         // Create the method.
         P(ast::ImplItem {
             id: ast::DUMMY_NODE_ID,
@@ -870,7 +879,7 @@ fn create_method(&self,
                 generics: fn_generics,
                 abi: abi,
                 explicit_self: explicit_self,
-                unsafety: ast::Unsafety::Normal,
+                unsafety: unsafety,
                 decl: fn_decl
             }, body_block)
         })
diff --git a/src/libsyntax/ext/deriving/hash.rs b/src/libsyntax/ext/deriving/hash.rs
index 698e788d65f..04387bd4b3f 100644
--- a/src/libsyntax/ext/deriving/hash.rs
+++ b/src/libsyntax/ext/deriving/hash.rs
@@ -44,6 +44,7 @@ pub fn expand_deriving_hash(cx: &mut ExtCtxt,
                 args: vec!(Ptr(Box::new(Literal(arg)), Borrowed(None, MutMutable))),
                 ret_ty: nil_ty(),
                 attributes: vec![],
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     hash_substructure(a, b, c)
                 }))
diff --git a/src/libsyntax/ext/deriving/primitive.rs b/src/libsyntax/ext/deriving/primitive.rs
index 4fe9aefa1a4..4aabcf04e41 100644
--- a/src/libsyntax/ext/deriving/primitive.rs
+++ b/src/libsyntax/ext/deriving/primitive.rs
@@ -44,6 +44,7 @@ pub fn expand_deriving_from_primitive(cx: &mut ExtCtxt,
                                            true)),
                 // #[inline] liable to cause code-bloat
                 attributes: attrs.clone(),
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(|c, s, sub| {
                     cs_from("i64", c, s, sub)
                 })),
@@ -59,6 +60,7 @@ pub fn expand_deriving_from_primitive(cx: &mut ExtCtxt,
                                            true)),
                 // #[inline] liable to cause code-bloat
                 attributes: attrs,
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(|c, s, sub| {
                     cs_from("u64", c, s, sub)
                 })),
diff --git a/src/libsyntax/ext/deriving/show.rs b/src/libsyntax/ext/deriving/show.rs
index dc634df2073..518bd161c1e 100644
--- a/src/libsyntax/ext/deriving/show.rs
+++ b/src/libsyntax/ext/deriving/show.rs
@@ -42,6 +42,7 @@ pub fn expand_deriving_show(cx: &mut ExtCtxt,
                 args: vec!(fmtr),
                 ret_ty: Literal(path_std!(cx, core::fmt::Result)),
                 attributes: Vec::new(),
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(|a, b, c| {
                     show_substructure(a, b, c)
                 }))
diff --git a/src/test/auxiliary/custom_derive_plugin.rs b/src/test/auxiliary/custom_derive_plugin.rs
index 0edbeb2d02c..b130c42dcd7 100644
--- a/src/test/auxiliary/custom_derive_plugin.rs
+++ b/src/test/auxiliary/custom_derive_plugin.rs
@@ -54,6 +54,7 @@ fn expand(cx: &mut ExtCtxt,
                 args: vec![],
                 ret_ty: Literal(Path::new_local("isize")),
                 attributes: vec![],
+                is_unsafe: false,
                 combine_substructure: combine_substructure(box |cx, span, substr| {
                     let zero = cx.expr_isize(span, 0);
                     cs_fold(false,
diff --git a/src/test/auxiliary/custom_derive_plugin_attr.rs b/src/test/auxiliary/custom_derive_plugin_attr.rs
index 92963b2812d..b056d8b5654 100644
--- a/src/test/auxiliary/custom_derive_plugin_attr.rs
+++ b/src/test/auxiliary/custom_derive_plugin_attr.rs
@@ -56,6 +56,7 @@ fn expand(cx: &mut ExtCtxt,
                 args: vec![],
                 ret_ty: Literal(Path::new_local("isize")),
                 attributes: vec![],
+                is_unsafe: false,
                 combine_substructure: combine_substructure(Box::new(totalsum_substructure)),
             },
         ],