diff --git a/.release-please-manifest.json b/.release-please-manifest.json
index b1b5a42f0..18807ca3b 100644
--- a/.release-please-manifest.json
+++ b/.release-please-manifest.json
@@ -1,3 +1,3 @@
 {
-  ".": "0.361.0"
+  ".": "0.361.1"
 }
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8f53a451c..eb97ac806 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # Changelog
 
+## 0.361.1 (2025-11-13)
+
+Full Changelog: [v0.361.0...v0.361.1](https://github.com/Increase/increase-java/compare/v0.361.0...v0.361.1)
+
+### Bug Fixes
+
+* **client:** multi-value header serialization ([5bec988](https://github.com/Increase/increase-java/commit/5bec988e759471ee0f3a8af6173636866a44ade7))
+
 ## 0.361.0 (2025-11-12)
 
 Full Changelog: [v0.360.0...v0.361.0](https://github.com/Increase/increase-java/compare/v0.360.0...v0.361.0)
diff --git a/README.md b/README.md
index bfe30e4a3..d8c70f275 100644
--- a/README.md
+++ b/README.md
@@ -2,8 +2,8 @@
 
 <!-- x-release-please-start-version -->
 
-[![Maven Central](https://img.shields.io/maven-central/v/com.increase.api/increase-java)](https://central.sonatype.com/artifact/com.increase.api/increase-java/0.361.0)
-[![javadoc](https://javadoc.io/badge2/com.increase.api/increase-java/0.361.0/javadoc.svg)](https://javadoc.io/doc/com.increase.api/increase-java/0.361.0)
+[![Maven Central](https://img.shields.io/maven-central/v/com.increase.api/increase-java)](https://central.sonatype.com/artifact/com.increase.api/increase-java/0.361.1)
+[![javadoc](https://javadoc.io/badge2/com.increase.api/increase-java/0.361.1/javadoc.svg)](https://javadoc.io/doc/com.increase.api/increase-java/0.361.1)
 
 <!-- x-release-please-end -->
 
@@ -13,7 +13,7 @@ The Increase Java SDK is similar to the Increase Kotlin SDK but with minor diffe
 
 <!-- x-release-please-start-version -->
 
-The REST API documentation can be found on [increase.com](https://increase.com/documentation). Javadocs are available on [javadoc.io](https://javadoc.io/doc/com.increase.api/increase-java/0.361.0).
+The REST API documentation can be found on [increase.com](https://increase.com/documentation). Javadocs are available on [javadoc.io](https://javadoc.io/doc/com.increase.api/increase-java/0.361.1).
 
 <!-- x-release-please-end -->
 
@@ -24,7 +24,7 @@ The REST API documentation can be found on [increase.com](https://increase.com/d
 ### Gradle
 
 ```kotlin
-implementation("com.increase.api:increase-java:0.361.0")
+implementation("com.increase.api:increase-java:0.361.1")
 ```
 
 ### Maven
@@ -33,7 +33,7 @@ implementation("com.increase.api:increase-java:0.361.0")
 <dependency>
   <groupId>com.increase.api</groupId>
   <artifactId>increase-java</artifactId>
-  <version>0.361.0</version>
+  <version>0.361.1</version>
 </dependency>
 ```
 
diff --git a/build.gradle.kts b/build.gradle.kts
index 20f17a4bf..731d73d9b 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -8,7 +8,7 @@ repositories {
 
 allprojects {
     group = "com.increase.api"
-    version = "0.361.0" // x-release-please-version
+    version = "0.361.1" // x-release-please-version
 }
 
 subprojects {
diff --git a/increase-java-client-okhttp/src/main/kotlin/com/increase/api/client/okhttp/OkHttpClient.kt b/increase-java-client-okhttp/src/main/kotlin/com/increase/api/client/okhttp/OkHttpClient.kt
index a94bf6a54..fa78a9f40 100644
--- a/increase-java-client-okhttp/src/main/kotlin/com/increase/api/client/okhttp/OkHttpClient.kt
+++ b/increase-java-client-okhttp/src/main/kotlin/com/increase/api/client/okhttp/OkHttpClient.kt
@@ -109,19 +109,19 @@ class OkHttpClient private constructor(private val okHttpClient: okhttp3.OkHttpC
 
         val builder = Request.Builder().url(toUrl()).method(method.name, body)
         headers.names().forEach { name ->
-            headers.values(name).forEach { builder.header(name, it) }
+            headers.values(name).forEach { builder.addHeader(name, it) }
         }
 
         if (
             !headers.names().contains("X-Stainless-Read-Timeout") && client.readTimeoutMillis != 0
         ) {
-            builder.header(
+            builder.addHeader(
                 "X-Stainless-Read-Timeout",
                 Duration.ofMillis(client.readTimeoutMillis.toLong()).seconds.toString(),
             )
         }
         if (!headers.names().contains("X-Stainless-Timeout") && client.callTimeoutMillis != 0) {
-            builder.header(
+            builder.addHeader(
                 "X-Stainless-Timeout",
                 Duration.ofMillis(client.callTimeoutMillis.toLong()).seconds.toString(),
             )