diff --git a/README.md b/README.md
index 363387fe..aeaeda74 100644
--- a/README.md
+++ b/README.md
@@ -87,7 +87,7 @@ let mut header = Header::new(Algorithm::HS512);
 header.kid = Some("blabla".to_owned());
 
 let mut extras = HashMap::with_capacity(1);
-extras.insert("custom".to_string(), "header".to_string());
+extras.insert("custom".to_string(), serde_json::Value::String("header".to_string()));
 header.extras = Some(extras);
 
 let token = encode(&header, &my_claims, &EncodingKey::from_secret("secret".as_ref()))?;
diff --git a/benches/jwt.rs b/benches/jwt.rs
index 6397d249..2fa78317 100644
--- a/benches/jwt.rs
+++ b/benches/jwt.rs
@@ -22,7 +22,7 @@ fn bench_encode_custom_extra_headers(c: &mut Criterion) {
     let claim = Claims { sub: "b@b.com".to_owned(), company: "ACME".to_owned() };
     let key = EncodingKey::from_secret("secret".as_ref());
     let mut extras = HashMap::with_capacity(1);
-    extras.insert("custom".to_string(), "header".to_string());
+    extras.insert("custom".to_string(), serde_json::Value::String("header".to_string()));
     let header = &Header { extras, ..Default::default() };
 
     c.bench_function("bench_encode", |b| {
diff --git a/examples/custom_header.rs b/examples/custom_header.rs
index 7c343d8f..ff27a305 100644
--- a/examples/custom_header.rs
+++ b/examples/custom_header.rs
@@ -17,7 +17,7 @@ fn main() {
     let key = b"secret";
 
     let mut extras = HashMap::with_capacity(1);
-    extras.insert("custom".to_string(), "header".to_string());
+    extras.insert("custom".to_string(), serde_json::Value::String("header".to_string()));
 
     let header = Header {
         kid: Some("signing_key".to_owned()),
diff --git a/src/header.rs b/src/header.rs
index 76b744a2..1fadc465 100644
--- a/src/header.rs
+++ b/src/header.rs
@@ -187,7 +187,7 @@ pub struct Header {
     /// Once serialized, all keys will be converted to fields at the root level of the header payload
     /// Ex: Dict("custom" -> "header") will be converted to "{"typ": "JWT", ..., "custom": "header"}"
     #[serde(flatten)]
-    pub extras: HashMap<String, String>,
+    pub extras: HashMap<String, serde_json::Value>,
 }
 
 impl Header {
diff --git a/tests/hmac.rs b/tests/hmac.rs
index f4f5968d..ff372930 100644
--- a/tests/hmac.rs
+++ b/tests/hmac.rs
@@ -68,7 +68,7 @@ fn encode_with_extra_custom_header() {
         exp: OffsetDateTime::now_utc().unix_timestamp() + 10000,
     };
     let mut extras = HashMap::with_capacity(1);
-    extras.insert("custom".to_string(), "header".to_string());
+    extras.insert("custom".to_string(), serde_json::Value::String("header".to_string()));
     let header = Header { kid: Some("kid".to_string()), extras, ..Default::default() };
     let token = encode(&header, &my_claims, &EncodingKey::from_secret(b"secret")).unwrap();
     let token_data = decode::<Claims>(
@@ -79,7 +79,7 @@ fn encode_with_extra_custom_header() {
     .unwrap();
     assert_eq!(my_claims, token_data.claims);
     assert_eq!("kid", token_data.header.kid.unwrap());
-    assert_eq!("header", token_data.header.extras.get("custom").unwrap().as_str());
+    assert_eq!("header", token_data.header.extras.get("custom").unwrap().as_str().unwrap());
 }
 
 #[test]
@@ -91,8 +91,8 @@ fn encode_with_multiple_extra_custom_headers() {
         exp: OffsetDateTime::now_utc().unix_timestamp() + 10000,
     };
     let mut extras = HashMap::with_capacity(2);
-    extras.insert("custom1".to_string(), "header1".to_string());
-    extras.insert("custom2".to_string(), "header2".to_string());
+    extras.insert("custom1".to_string(), serde_json::Value::String("header1".to_string()));
+    extras.insert("custom2".to_string(), serde_json::Value::String("header2".to_string()));
     let header = Header { kid: Some("kid".to_string()), extras, ..Default::default() };
     let token = encode(&header, &my_claims, &EncodingKey::from_secret(b"secret")).unwrap();
     let token_data = decode::<Claims>(
@@ -104,8 +104,8 @@ fn encode_with_multiple_extra_custom_headers() {
     assert_eq!(my_claims, token_data.claims);
     assert_eq!("kid", token_data.header.kid.unwrap());
     let extras = token_data.header.extras;
-    assert_eq!("header1", extras.get("custom1").unwrap().as_str());
-    assert_eq!("header2", extras.get("custom2").unwrap().as_str());
+    assert_eq!("header1", extras.get("custom1").unwrap().as_str().unwrap());
+    assert_eq!("header2", extras.get("custom2").unwrap().as_str().unwrap());
 }
 
 #[test]
@@ -156,8 +156,25 @@ fn decode_token_custom_headers() {
     assert_eq!(my_claims, claims.claims);
     assert_eq!("kid", claims.header.kid.unwrap());
     let extras = claims.header.extras;
-    assert_eq!("header1", extras.get("custom1").unwrap().as_str());
-    assert_eq!("header2", extras.get("custom2").unwrap().as_str());
+    assert_eq!("header1", extras.get("custom1").unwrap().as_str().unwrap());
+    assert_eq!("header2", extras.get("custom2").unwrap().as_str().unwrap());
+}
+
+#[test]
+#[wasm_bindgen_test]
+fn decode_token_with_non_string_extra_header() {
+    // Header: {"typ":"JWT","alg":"HS256","uid":180444}
+    // This token has an integer value in the header extras which previously
+    // caused deserialization to fail when extras was HashMap<String, String>.
+    let token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiIsInVpZCI6MTgwNDQ0fQ.eyJzdWIiOiJiQGIuY29tIiwiY29tcGFueSI6IkFDTUUiLCJleHAiOjI1MzI1MjQ4OTF9.orW-ZcVTziQ99c8lg5LcQk9YxITxS47pHWv-3nwcAhI";
+    let claims = decode::<Claims>(
+        token,
+        &DecodingKey::from_secret(b"secret"),
+        &Validation::new(Algorithm::HS256),
+    );
+    assert!(claims.is_ok());
+    let token_data = claims.unwrap();
+    assert_eq!(180444, token_data.header.extras.get("uid").unwrap().as_u64().unwrap());
 }
 
 #[test]