diff --git a/serde/src/de/mod.rs b/serde/src/de/mod.rs
index d8b860b2..eac50313 100644
--- a/serde/src/de/mod.rs
+++ b/serde/src/de/mod.rs
@@ -101,6 +101,8 @@ use std::error;
 use collections::{String, Vec};
 
 use core::fmt::{self, Display};
+#[cfg(not(feature = "std"))]
+use core::fmt::Debug;
 use core::marker::PhantomData;
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -122,7 +124,7 @@ pub use self::ignored_any::IgnoredAny;
 ///////////////////////////////////////////////////////////////////////////////
 
 macro_rules! declare_error_trait {
-    (Error: Sized $(+ $($supertrait:ident)::*)*) => {
+    (Error: Sized $(+ $($supertrait:ident)::+)*) => {
         /// The `Error` trait allows `Deserialize` implementations to create descriptive
         /// error messages belonging to the `Deserializer` against which they are
         /// currently running.
@@ -136,7 +138,7 @@ macro_rules! declare_error_trait {
         ///
         /// Most deserializers should only need to provide the `Error::custom` method
         /// and inherit the default behavior for the other methods.
-        pub trait Error: Sized $(+ $($supertrait)::*)* {
+        pub trait Error: Sized $(+ $($supertrait)::+)* {
             /// Raised when there is general error when deserializing a type.
             ///
             /// The message should not be capitalized and should not end with a period.
@@ -254,7 +256,7 @@ macro_rules! declare_error_trait {
 declare_error_trait!(Error: Sized + error::Error);
 
 #[cfg(not(feature = "std"))]
-declare_error_trait!(Error: Sized);
+declare_error_trait!(Error: Sized + Debug + Display);
 
 /// `Unexpected` represents an unexpected invocation of any one of the `Visitor`
 /// trait methods.
diff --git a/serde/src/ser/mod.rs b/serde/src/ser/mod.rs
index 63065e09..5c4f81a9 100644
--- a/serde/src/ser/mod.rs
+++ b/serde/src/ser/mod.rs
@@ -97,6 +97,8 @@ use std::error;
 
 #[cfg(all(feature = "collections", not(feature = "std")))]
 use collections::string::String;
+#[cfg(not(feature = "std"))]
+use core::fmt::Debug;
 use core::fmt::Display;
 #[cfg(any(feature = "std", feature = "collections"))]
 use core::fmt::Write;
@@ -116,11 +118,11 @@ pub use self::impossible::Impossible;
 ///////////////////////////////////////////////////////////////////////////////
 
 macro_rules! declare_error_trait {
-    (Error: Sized $(+ $($supertrait:ident)::*)*) => {
+    (Error: Sized $(+ $($supertrait:ident)::+)*) => {
         /// Trait used by `Serialize` implementations to generically construct
         /// errors belonging to the `Serializer` against which they are
         /// currently running.
-        pub trait Error: Sized $(+ $($supertrait)::*)* {
+        pub trait Error: Sized $(+ $($supertrait)::+)* {
             /// Raised when a `Serialize` implementation encounters a general
             /// error while serializing a type.
             ///
@@ -154,7 +156,7 @@ macro_rules! declare_error_trait {
 declare_error_trait!(Error: Sized + error::Error);
 
 #[cfg(not(feature = "std"))]
-declare_error_trait!(Error: Sized);
+declare_error_trait!(Error: Sized + Debug + Display);
 
 ///////////////////////////////////////////////////////////////////////////////