diff --git a/Cargo.lock b/Cargo.lock
index 2685b6e..bb05bc1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -45,6 +45,7 @@ name = "docx-core"
 version = "0.1.0"
 dependencies = [
  "pretty_assertions 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "thiserror 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasm-bindgen 0.2.53 (registry+https://github.com/rust-lang/crates.io-index)",
  "xml-rs 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "zip 0.5.3 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -121,6 +122,24 @@ dependencies = [
  "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "thiserror"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "thiserror-impl 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "unicode-xid"
 version = "0.2.0"
@@ -223,6 +242,8 @@ dependencies = [
 "checksum proc-macro2 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)" = "9c9e470a8dc4aeae2dee2f335e8f533e2d4b347e1434e5671afc49b054592f27"
 "checksum quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "053a8c8bcc71fcce321828dc897a98ab9760bef03a4fc36693c231e5b3216cfe"
 "checksum syn 1.0.7 (registry+https://github.com/rust-lang/crates.io-index)" = "0e7bedb3320d0f3035594b0b723c8a28d7d336a3eda3881db79e61d676fb644c"
+"checksum thiserror 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)" = "f9fb62ff737e573b1e677459bea6fd023cd5d6e868c3242d3cdf3ef2f0554824"
+"checksum thiserror-impl 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)" = "24069c0ba08aab54289d6a25f5036d94afc61e1538bbc42ae5501df141c9027d"
 "checksum unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
 "checksum wasm-bindgen 0.2.53 (registry+https://github.com/rust-lang/crates.io-index)" = "4c29d57d5c3b3bc53bbe35c5a4f4a0df994d870b7d3cb0ad1c2065e21822ae41"
 "checksum wasm-bindgen-backend 0.2.53 (registry+https://github.com/rust-lang/crates.io-index)" = "aa2868fa93e5bf36a9364d1277a0f97392748a8217d9aa0ec3f1cdbdf7ad1a60"
diff --git a/docx-core/Cargo.toml b/docx-core/Cargo.toml
index bc797c3..7a003fa 100644
--- a/docx-core/Cargo.toml
+++ b/docx-core/Cargo.toml
@@ -9,6 +9,7 @@ edition = "2018"
 [dependencies]
 xml-rs = "0.8.0"
 wasm-bindgen = "0.2.50"
+thiserror = "1.0"
 zip = { version = "0.5", default-features = false }
 
 [dev-dependencies]
diff --git a/docx-core/examples/alignment.rs b/docx-core/examples/alignment.rs
index ade39aa..be34a2e 100644
--- a/docx-core/examples/alignment.rs
+++ b/docx-core/examples/alignment.rs
@@ -1,6 +1,6 @@
 use docx_core::*;
 
-pub fn main() {
+pub fn main() -> Result<(), DocxError> {
   let path = std::path::Path::new("./output/alignment.docx");
   let file = std::fs::File::create(&path).unwrap();
   Docx::new()
@@ -11,5 +11,6 @@ pub fn main() {
         .align(AlignmentType::Right),
     )
     .build()
-    .pack(file);
+    .pack(file)?;
+  Ok(())
 }
diff --git a/docx-core/examples/example.rs b/docx-core/examples/example.rs
deleted file mode 100644
index 9a850eb..0000000
--- a/docx-core/examples/example.rs
+++ /dev/null
@@ -1,5 +0,0 @@
-extern crate docx_core;
-
-fn main() {
-  docx_core::simple();
-}
\ No newline at end of file
diff --git a/docx-core/examples/indent.rs b/docx-core/examples/indent.rs
index e0e4aa0..1cfa8e6 100644
--- a/docx-core/examples/indent.rs
+++ b/docx-core/examples/indent.rs
@@ -2,7 +2,7 @@ use docx_core::*;
 
 pub const DUMMY: &str = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.";
 
-pub fn main() {
+pub fn main() -> Result<(), DocxError> {
   let path = std::path::Path::new("./output/indent.docx");
   let file = std::fs::File::create(&path).unwrap();
   Docx::new()
@@ -20,5 +20,6 @@ pub fn main() {
         .indent(1560, Some(SpecialIndentType::Hanging(720))),
     )
     .build()
-    .pack(file);
+    .pack(file)?;
+  Ok(())
 }
diff --git a/docx-core/examples/size.rs b/docx-core/examples/size.rs
index 6a36a0b..40f39f6 100644
--- a/docx-core/examples/size.rs
+++ b/docx-core/examples/size.rs
@@ -1,6 +1,6 @@
 use docx_core::*;
 
-pub fn main() {
+pub fn main() -> Result<(), DocxError> {
   let path = std::path::Path::new("./output/size.docx");
   let file = std::fs::File::create(&path).unwrap();
   Docx::new()
@@ -11,5 +11,6 @@ pub fn main() {
         .add_run(Run::new("ld")),
     )
     .build()
-    .pack(file);
+    .pack(file)?;
+  Ok(())
 }
diff --git a/docx-core/src/errors/mod.rs b/docx-core/src/errors/mod.rs
new file mode 100644
index 0000000..9c0e5ea
--- /dev/null
+++ b/docx-core/src/errors/mod.rs
@@ -0,0 +1,11 @@
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum DocxError {
+    #[error("Failed to write XML to buffer.")]
+    EmitterError(#[from] xml::writer::Error),
+    #[error("Failed to zip XML documents.")]
+    ZipError(#[from] zip::result::ZipError),
+    #[error("Unknown error")]
+    Unknown,
+}
diff --git a/docx-core/src/lib.rs b/docx-core/src/lib.rs
index bf5883d..9bdd3fe 100644
--- a/docx-core/src/lib.rs
+++ b/docx-core/src/lib.rs
@@ -1,11 +1,12 @@
 mod documents;
+mod errors;
 mod types;
 mod xml_builder;
 mod zipper;
 
 pub use documents::*;
+pub use errors::*;
 pub use types::*;
-pub use zipper::*;
 
 pub fn simple() {
     let path = std::path::Path::new("./test.docx");
diff --git a/docx-core/src/xml_builder/mod.rs b/docx-core/src/xml_builder/mod.rs
index 5119a13..32d74d9 100644
--- a/docx-core/src/xml_builder/mod.rs
+++ b/docx-core/src/xml_builder/mod.rs
@@ -93,6 +93,7 @@ impl XMLBuilder {
     }
 
     // Write plain text
+    #[allow(dead_code)]
     pub(crate) fn plain_text(mut self, t: &str) -> Self {
         self.writer.write(t).unwrap();
         self
diff --git a/docx-wasm/src/lib.rs b/docx-wasm/src/lib.rs
index 1bbd9a6..e4aa435 100644
--- a/docx-wasm/src/lib.rs
+++ b/docx-wasm/src/lib.rs
@@ -20,12 +20,14 @@ impl Docx {
         self
     }
 
-    pub fn build(&self) -> Vec<u8> {
+    pub fn build(&self) -> Result<Vec<u8>, JsValue> {
         let buf = Vec::new();
         let mut cur = std::io::Cursor::new(buf);
-        let b = self.0.build();
-        docx_core::zip(&mut cur, b).unwrap();
-        cur.into_inner()
+        let res = self.0.build().pack(&mut cur);
+        if res.is_err() {
+            return Err(format!("{:?}", res).into());
+        }
+        Ok(cur.into_inner())
     }
 
     pub fn test(&self, t: docx_core::StyleType) {