diff --git a/lettre/Cargo.toml b/lettre/Cargo.toml
index 8b7c5a3..d79cc0f 100644
--- a/lettre/Cargo.toml
+++ b/lettre/Cargo.toml
@@ -20,7 +20,7 @@ is-it-maintained-open-issues = { repository = "lettre/lettre" }
 
 [dependencies]
 log = "^0.4"
-nom = { version = "^3.2", optional = true }
+nom = { version = "^4.0", optional = true }
 bufstream = { version = "^0.1", optional = true }
 native-tls = { version = "^0.1", optional = true }
 base64 = { version = "^0.9", optional = true }
diff --git a/lettre/src/smtp/error.rs b/lettre/src/smtp/error.rs
index b74d24b..628ed22 100644
--- a/lettre/src/smtp/error.rs
+++ b/lettre/src/smtp/error.rs
@@ -37,7 +37,7 @@ pub enum Error {
     /// TLS error
     Tls(native_tls::Error),
     /// Parsing error
-    Parsing(nom::simple_errors::Err),
+    Parsing(nom::ErrorKind),
 }
 
 impl Display for Error {
@@ -77,7 +77,7 @@ impl StdError for Error {
             Utf8Parsing(ref err) => Some(&*err),
             Io(ref err) => Some(&*err),
             Tls(ref err) => Some(&*err),
-            Parsing(ref err) => Some(&*err),
+            Parsing(_) => None,
             _ => None,
         }
     }
@@ -95,8 +95,8 @@ impl From<native_tls::Error> for Error {
     }
 }
 
-impl From<nom::simple_errors::Err> for Error {
-    fn from(err: nom::simple_errors::Err) -> Error {
+impl From<nom::ErrorKind> for Error {
+    fn from(err: nom::ErrorKind) -> Error {
         Parsing(err)
     }
 }
diff --git a/lettre/src/smtp/response.rs b/lettre/src/smtp/response.rs
index c4299f1..f7a72ec 100644
--- a/lettre/src/smtp/response.rs
+++ b/lettre/src/smtp/response.rs
@@ -1,8 +1,7 @@
 //! SMTP response, containing a mandatory return code and an optional text
 //! message
 
-use nom::{crlf, ErrorKind as NomErrorKind, IResult as NomResult};
-use nom::simple_errors::Err as NomError;
+use nom::{crlf, ErrorKind as NomErrorKind};
 use std::fmt::{Display, Formatter, Result};
 use std::result;
 use std::str::{FromStr, from_utf8};
@@ -126,13 +125,12 @@ pub struct Response {
 }
 
 impl FromStr for Response {
-    type Err = NomError;
+    type Err = NomErrorKind;
 
-    fn from_str(s: &str) -> result::Result<Response, NomError> {
+    fn from_str(s: &str) -> result::Result<Response, NomErrorKind> {
         match parse_response(s.as_bytes()) {
-            NomResult::Done(_, res) => Ok(res),
-            NomResult::Error(e) => Err(e),
-            NomResult::Incomplete(_) => Err(NomErrorKind::Complete),
+            Ok((_, res)) => Ok(res),
+            Err(e) => Err(e.into_error_kind()),
         }
     }
 }