diff --git a/gradient-labs-client/src/main/java/ai/gradientlabs/client/request/FinishConversationRequest.java b/gradient-labs-client/src/main/java/ai/gradientlabs/client/request/FinishConversationRequest.java
index 19b7623..a06ac92 100644
--- a/gradient-labs-client/src/main/java/ai/gradientlabs/client/request/FinishConversationRequest.java
+++ b/gradient-labs-client/src/main/java/ai/gradientlabs/client/request/FinishConversationRequest.java
@@ -12,8 +12,12 @@ public class FinishConversationRequest {
     @JsonProperty("reason")
     private final String reason;
 
+    @JsonProperty("reason_code")
+    private final String reasonCode;
+
     private FinishConversationRequest(Builder builder) {
         this.reason = builder.reason;
+        this.reasonCode = builder.reasonCode;
     }
 
     public static Builder builder() {
@@ -28,8 +32,13 @@ public String getReason() {
         return reason;
     }
 
+    public String getReasonCode() {
+        return reasonCode;
+    }
+
     public static class Builder {
         private String reason;
+        private String reasonCode;
 
         private Builder() {
         }
@@ -39,6 +48,11 @@ public Builder reason(String reason) {
             return this;
         }
 
+        public Builder reasonCode(String reasonCode) {
+            this.reasonCode = reasonCode;
+            return this;
+        }
+
         public FinishConversationRequest build() {
             return new FinishConversationRequest(this);
         }
diff --git a/gradient-labs-client/src/test/java/ai/gradientlabs/client/request/FinishConversationRequestTest.java b/gradient-labs-client/src/test/java/ai/gradientlabs/client/request/FinishConversationRequestTest.java
new file mode 100644
index 0000000..ccec68c
--- /dev/null
+++ b/gradient-labs-client/src/test/java/ai/gradientlabs/client/request/FinishConversationRequestTest.java
@@ -0,0 +1,39 @@
+package ai.gradientlabs.client.request;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+class FinishConversationRequestTest {
+
+    private final ObjectMapper objectMapper = new ObjectMapper().registerModule(new JavaTimeModule());
+
+    @Test
+    void serializesReasonCode() throws Exception {
+        FinishConversationRequest request = FinishConversationRequest.builder()
+                .reason("The customer said goodbye")
+                .reasonCode("customer-ended-chat")
+                .build();
+
+        JsonNode json = objectMapper.valueToTree(request);
+
+        assertEquals("The customer said goodbye", json.get("reason").asText());
+        assertEquals("customer-ended-chat", json.get("reason_code").asText());
+        assertEquals("customer-ended-chat", request.getReasonCode());
+    }
+
+    @Test
+    void omitsReasonCodeWhenNotSet() throws Exception {
+        FinishConversationRequest request = FinishConversationRequest.builder()
+                .reason("The customer said goodbye")
+                .build();
+
+        JsonNode json = objectMapper.valueToTree(request);
+
+        assertFalse(json.has("reason_code"));
+    }
+}