diff --git a/codegen/build.rs b/codegen/build.rs
index 5d108b0c..6e57575c 100644
--- a/codegen/build.rs
+++ b/codegen/build.rs
@@ -8,8 +8,8 @@ use yansi::Color::{Red, Yellow, Blue, White};
 use version_check::{supports_features, is_min_version, is_min_date};
 
 // Specifies the minimum nightly version needed to compile Rocket's codegen.
-const MIN_DATE: &'static str = "2018-06-22";
-const MIN_VERSION: &'static str = "1.28.0-nightly";
+const MIN_DATE: &'static str = "2018-07-15";
+const MIN_VERSION: &'static str = "1.29.0-nightly";
 
 fn main() {
     let ok_channel = supports_features();
diff --git a/codegen/src/decorators/derive_form.rs b/codegen/src/decorators/derive_form.rs
index 39430e37..7f65e7de 100644
--- a/codegen/src/decorators/derive_form.rs
+++ b/codegen/src/decorators/derive_form.rs
@@ -15,7 +15,7 @@ use syntax_ext::deriving::generic::MethodDef;
 use syntax_ext::deriving::generic::{StaticStruct, Substructure, TraitDef, ty};
 use syntax_ext::deriving::generic::combine_substructure as c_s;
 
-use utils::{strip_ty_lifetimes, is_valid_ident, SpanExt};
+use utils::{strip_ty_lifetimes, is_valid_ident, SpanExt, GenericParamExt};
 
 static ONLY_STRUCTS_ERR: &'static str = "`FromForm` can only be derived for \
     structures with named fields.";
@@ -26,7 +26,7 @@ fn struct_lifetime(ecx: &mut ExtCtxt, item: &Annotatable, sp: Span) -> Option<St
         Annotatable::Item(ref item) => match item.node {
             ItemKind::Struct(_, ref generics) => {
                 let mut lifetimes = generics.params.iter()
-                    .filter(|p| p.kind == GenericParamKind::Lifetime)
+                    .filter(|p| p.is_lifetime())
                     .map(|p| p.ident.to_string());
 
                 let lifetime = lifetimes.next();
diff --git a/codegen/src/utils/generics_ext.rs b/codegen/src/utils/generics_ext.rs
new file mode 100644
index 00000000..c2497e5a
--- /dev/null
+++ b/codegen/src/utils/generics_ext.rs
@@ -0,0 +1,15 @@
+use syntax::ast::{GenericParam, GenericParamKind};
+
+pub trait GenericParamExt {
+    /// Returns `true` if `self` is of kind `lifetime`.
+    fn is_lifetime(&self) -> bool;
+}
+
+impl GenericParamExt for GenericParam {
+    fn is_lifetime(&self) -> bool {
+        match self.kind {
+            GenericParamKind::Lifetime => true,
+            _ => false
+        }
+    }
+}
diff --git a/codegen/src/utils/mod.rs b/codegen/src/utils/mod.rs
index 75b4ef45..a610bb59 100644
--- a/codegen/src/utils/mod.rs
+++ b/codegen/src/utils/mod.rs
@@ -3,12 +3,14 @@ mod arg_ext;
 mod parser_ext;
 mod ident_ext;
 mod span_ext;
+mod generics_ext;
 
 pub use self::arg_ext::ArgExt;
 pub use self::meta_item_ext::MetaItemExt;
 pub use self::parser_ext::ParserExt;
 pub use self::ident_ext::IdentExt;
 pub use self::span_ext::SpanExt;
+pub use self::generics_ext::GenericParamExt;
 
 use std::convert::AsRef;