diff --git a/serde/src/de/mod.rs b/serde/src/de/mod.rs
index 56c422f24..a251e7159 100644
--- a/serde/src/de/mod.rs
+++ b/serde/src/de/mod.rs
@@ -12,7 +12,7 @@ mod from_primitive;
 /// `Deserializer` error.
 pub trait Error: Sized + error::Error {
     /// Raised when there is general error when deserializing a type.
-    fn custom(msg: String) -> Self;
+    fn custom<T: Into<String>>(msg: T) -> Self;
 
     /// Raised when a `Deserialize` type unexpectedly hit the end of the stream.
     fn end_of_stream() -> Self;
diff --git a/serde/src/de/value.rs b/serde/src/de/value.rs
index 773c19df3..791cb900f 100644
--- a/serde/src/de/value.rs
+++ b/serde/src/de/value.rs
@@ -50,7 +50,7 @@ pub enum Error {
 }
 
 impl de::Error for Error {
-    fn custom(msg: String) -> Self { Error::Custom(msg) }
+    fn custom<T: Into<String>>(msg: T) -> Self { Error::Custom(msg.into()) }
     fn end_of_stream() -> Self { Error::EndOfStream }
     fn invalid_type(ty: de::Type) -> Self { Error::InvalidType(ty) }
     fn invalid_value(msg: &str) -> Self { Error::InvalidValue(msg.to_owned()) }
diff --git a/serde/src/ser/mod.rs b/serde/src/ser/mod.rs
index 01368afb6..7129ebfb0 100644
--- a/serde/src/ser/mod.rs
+++ b/serde/src/ser/mod.rs
@@ -10,7 +10,7 @@ pub mod impls;
 /// `Serializer` error.
 pub trait Error: Sized + error::Error {
     /// Raised when there is general error when deserializing a type.
-    fn custom(msg: String) -> Self;
+    fn custom<T: Into<String>>(msg: T) -> Self;
 
     /// Raised when a `Serialize` was passed an incorrect value.
     fn invalid_value(msg: &str) -> Self {
diff --git a/serde_tests/benches/bench_enum.rs b/serde_tests/benches/bench_enum.rs
index 220f0de36..e5deaad77 100644
--- a/serde_tests/benches/bench_enum.rs
+++ b/serde_tests/benches/bench_enum.rs
@@ -22,7 +22,7 @@ pub enum Error {
 }
 
 impl serde::de::Error for Error {
-    fn custom(_: String) -> Error { Error::Syntax }
+    fn custom<T: Into<String>>(_: T) -> Error { Error::Syntax }
 
     fn end_of_stream() -> Error { Error::EndOfStream }
 
diff --git a/serde_tests/benches/bench_map.rs b/serde_tests/benches/bench_map.rs
index beab38f8d..32bc44150 100644
--- a/serde_tests/benches/bench_map.rs
+++ b/serde_tests/benches/bench_map.rs
@@ -19,7 +19,7 @@ pub enum Error {
 }
 
 impl serde::de::Error for Error {
-    fn custom(_: String) -> Error { Error::Syntax }
+    fn custom<T: Into<String>>(_: T) -> Error { Error::Syntax }
 
     fn end_of_stream() -> Error { Error::EndOfStream }
 
diff --git a/serde_tests/benches/bench_struct.rs b/serde_tests/benches/bench_struct.rs
index 7ad311f7d..402230d40 100644
--- a/serde_tests/benches/bench_struct.rs
+++ b/serde_tests/benches/bench_struct.rs
@@ -35,7 +35,7 @@ pub enum Error {
 }
 
 impl serde::de::Error for Error {
-    fn custom(_: String) -> Error { Error::Syntax }
+    fn custom<T: Into<String>>(_: T) -> Error { Error::Syntax }
 
     fn end_of_stream() -> Error { Error::EndOfStream }
 
diff --git a/serde_tests/benches/bench_vec.rs b/serde_tests/benches/bench_vec.rs
index 01edcf09e..96a4e6379 100644
--- a/serde_tests/benches/bench_vec.rs
+++ b/serde_tests/benches/bench_vec.rs
@@ -17,7 +17,7 @@ pub enum Error {
 }
 
 impl serde::de::Error for Error {
-    fn custom(_: String) -> Error { Error::Syntax }
+    fn custom<T: Into<String>>(_: T) -> Error { Error::Syntax }
 
     fn end_of_stream() -> Error { Error::EndOfStream }
 
diff --git a/serde_tests/tests/test_bytes.rs b/serde_tests/tests/test_bytes.rs
index 93fe97057..52e159f83 100644
--- a/serde_tests/tests/test_bytes.rs
+++ b/serde_tests/tests/test_bytes.rs
@@ -10,11 +10,11 @@ use serde::bytes::{ByteBuf, Bytes};
 struct Error;
 
 impl serde::ser::Error for Error {
-    fn custom(_: String) -> Error { Error }
+    fn custom<T: Into<String>>(_: T) -> Error { Error }
 }
 
 impl serde::de::Error for Error {
-    fn custom(_: String) -> Error { Error }
+    fn custom<T: Into<String>>(_: T) -> Error { Error }
 
     fn end_of_stream() -> Error { Error }
 }
diff --git a/serde_tests/tests/token.rs b/serde_tests/tests/token.rs
index 16be21b14..7a537a6ac 100644
--- a/serde_tests/tests/token.rs
+++ b/serde_tests/tests/token.rs
@@ -416,7 +416,7 @@ pub enum Error {
 }
 
 impl ser::Error for Error {
-    fn custom(_: String) -> Error { Error::SyntaxError }
+    fn custom<T: Into<String>>(_: T) -> Error { Error::SyntaxError }
 
     fn invalid_value(msg: &str) -> Error {
         Error::InvalidValue(msg.to_owned())
@@ -424,7 +424,7 @@ impl ser::Error for Error {
 }
 
 impl de::Error for Error {
-    fn custom(_: String) -> Error { Error::SyntaxError }
+    fn custom<T: Into<String>>(_: T) -> Error { Error::SyntaxError }
 
     fn end_of_stream() -> Error { Error::EndOfStreamError }