diff --git a/src/error_chain.rs b/src/error_chain.rs
index 83827096..799c7cad 100644
--- a/src/error_chain.rs
+++ b/src/error_chain.rs
@@ -231,7 +231,7 @@ macro_rules! impl_error_chain_processed {
 
             fn with_chain<E, K>(error: E, kind: K)
                 -> Self
-                where E: ::std::error::Error + Send + 'static,
+                where E: ::std::error::Error + Send + Sync + 'static,
                       K: Into<Self::ErrorKind>
             {
                 Self::with_chain(error, kind)
@@ -273,7 +273,7 @@ macro_rules! impl_error_chain_processed {
             /// Constructs a chained error from another error and a kind, and generates a backtrace.
             pub fn with_chain<E, K>(error: E, kind: K)
                 -> $error_name
-                where E: ::std::error::Error + Send + 'static,
+                where E: ::std::error::Error + Send + Sync + 'static,
                       K: Into<$error_kind_name>
             {
                 $error_name::with_boxed_chain(Box::new(error), kind)
@@ -281,7 +281,7 @@ macro_rules! impl_error_chain_processed {
 
             /// Construct a chained error from another boxed error and a kind, and generates a backtrace
             #[allow(unknown_lints, bare_trait_objects)]
-            pub fn with_boxed_chain<K>(error: Box<::std::error::Error + Send>, kind: K)
+            pub fn with_boxed_chain<K>(error: Box<::std::error::Error + Send + Sync>, kind: K)
                 -> $error_name
                 where K: Into<$error_kind_name>
             {
@@ -426,7 +426,7 @@ macro_rules! impl_error_chain_processed {
                       EK: Into<$error_kind_name>;
         }
 
-        impl<T, E> $result_ext_name<T> for ::std::result::Result<T, E> where E: ::std::error::Error + Send + 'static {
+        impl<T, E> $result_ext_name<T> for ::std::result::Result<T, E> where E: ::std::error::Error + Send + Sync + 'static {
             fn chain_err<F, EK>(self, callback: F) -> ::std::result::Result<T, $error_name>
                 where F: FnOnce() -> EK,
                       EK: Into<$error_kind_name> {
@@ -545,7 +545,7 @@ macro_rules! impl_extract_backtrace {
      $([$link_error_path: path, $(#[$meta_links: meta])*])*) => {
         #[allow(unknown_lints, renamed_and_removed_lints, bare_trait_objects)]
         #[allow(unused_doc_comment, unused_doc_comments)]
-        fn extract_backtrace(e: &(::std::error::Error + Send + 'static))
+        fn extract_backtrace(e: &(::std::error::Error + Send + Sync + 'static))
             -> Option<$crate::InternalBacktrace> {
             if let Some(e) = e.downcast_ref::<$error_name>() {
                 return Some(e.1.backtrace.clone());
diff --git a/src/lib.rs b/src/lib.rs
index b6bd2f27..74b1138d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -592,7 +592,7 @@ impl<'a> Iterator for Iter<'a> {
 
 /// This trait is implemented on all the errors generated by the `error_chain`
 /// macro.
-pub trait ChainedError: error::Error + Send + 'static {
+pub trait ChainedError: error::Error + Send + Sync + 'static {
     /// Associated kind type.
     type ErrorKind;
 
@@ -605,7 +605,7 @@ pub trait ChainedError: error::Error + Send + 'static {
     fn with_chain<E, K>(error: E, kind: K) -> Self
     where
         Self: Sized,
-        E: ::std::error::Error + Send + 'static,
+        E: ::std::error::Error + Send + Sync + 'static,
         K: Into<Self::ErrorKind>;
 
     /// Returns the kind of the error.
@@ -641,7 +641,7 @@ pub trait ChainedError: error::Error + Send + 'static {
     /// of the errors from `foreign_links`.
     #[doc(hidden)]
     #[allow(unknown_lints, bare_trait_objects)]
-    fn extract_backtrace(e: &(error::Error + Send + 'static)) -> Option<InternalBacktrace>
+    fn extract_backtrace(e: &(error::Error + Send + Sync + 'static)) -> Option<InternalBacktrace>
     where
         Self: Sized;
 }
@@ -675,7 +675,7 @@ where
 #[allow(unknown_lints, bare_trait_objects)]
 pub struct State {
     /// Next error in the error chain.
-    pub next_error: Option<Box<error::Error + Send>>,
+    pub next_error: Option<Box<error::Error + Send + Sync>>,
     /// Backtrace for the current error.
     pub backtrace: InternalBacktrace,
 }
@@ -692,7 +692,7 @@ impl Default for State {
 impl State {
     /// Creates a new State type
     #[allow(unknown_lints, bare_trait_objects)]
-    pub fn new<CE: ChainedError>(e: Box<error::Error + Send>) -> State {
+    pub fn new<CE: ChainedError>(e: Box<error::Error + Send + Sync>) -> State {
         let backtrace = CE::extract_backtrace(&*e).unwrap_or_else(InternalBacktrace::new);
         State {
             next_error: Some(e),