diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 34f1d36..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,19 +0,0 @@
-os:
-  - linux
-  - osx
-  - windows
-language: rust
-install:
-  - if [ $TRAVIS_OS_NAME = windows ]; then rustup toolchain install stable-msvc && rustup default stable-msvc; fi
-script:
-  - cargo build --verbose --all
-  - cargo test --verbose test::test_ffi
-  - cargo test --verbose test::test_natpmp
-  - cargo doc --verbose
-deploy:
-  provider: cargo
-  on:
-    tags: true
-    condition: $TRAVIS_OS_NAME = linux
-  token:
-    secure: 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
diff --git a/Cargo.toml b/Cargo.toml
index c515154..0860ee7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "natpmp"
-version = "0.3.2"
+version = "0.3.3"
 authors = ["fengyingcai <fengyc.work@gmail.com>"]
 description = "NAT-PMP client library"
 homepage = "https://github.com/fengyc/natpmp"
diff --git a/src/error.rs b/src/error.rs
index 7b8c71b..69dbba1 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -111,3 +111,5 @@ impl fmt::Display for Error {
         }
     }
 }
+
+impl std::error::Error for Error {}