diff --git a/src/types.rs b/src/types.rs
index 8fa5cd1..05f3bd5 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -62,23 +62,19 @@ pub enum Part {
 
 pub type GenerateContentResponse = Vec<ResponseStreamChunk>;
 
-// #[derive(Debug, Serialize, Deserialize)]
-// #[serde(rename_all = "camelCase")]
-// #[serde(untagged)]
-// pub enum ResponseStreamChunkType {
-//     Ok {
-//         candidates: Vec<Candidate>,
-//         usage_metadata: UsageMetadata,
-//     },
-//     Error,
-// }
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+#[serde(untagged)]
+pub enum ResponseStreamChunk {
+    Ok(OkResponse),
+    Error(Error),
+}
 
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
-pub struct ResponseStreamChunk {
-    pub candidates: Option<Vec<Candidate>>,
-    pub usage_metadata: Option<UsageMetadata>,
-    pub error: Option<Error>,
+pub struct OkResponse {
+    pub candidates: Vec<Candidate>,
+    pub usage_metadata: UsageMetadata,
 }
 
 #[derive(Debug, Serialize, Deserialize)]
diff --git a/src/vertex_client.rs b/src/vertex_client.rs
index 27b169d..dc54405 100644
--- a/src/vertex_client.rs
+++ b/src/vertex_client.rs
@@ -2,6 +2,7 @@ use crate::conversation::{Message, Role};
 use crate::error::{Error, Result};
 use crate::prelude::{
     Content, Conversation, GenerateContentRequest, GenerateContentResponse, GenerationConfig,
+    ResponseStreamChunk,
 };
 use crate::{prelude::Part, token_provider::TokenProvider};
 
@@ -94,32 +95,7 @@ impl<T: TokenProvider + Clone> VertexClient<T> {
             .await?;
 
         // Check for errors in the response.
-        for chunk in &response {
-            if let Some(error) = &chunk.error {
-                tracing::error!("Error in response: {:?}", error);
-                let cloned = error.clone();
-                return Err(Error::VertexError(cloned));
-            }
-        }
-
-        let text = response
-            .into_iter()
-            .flat_map(|chunk| {
-                chunk.candidates.unwrap().into_iter().flat_map(|candidate| {
-                    candidate
-                        .content
-                        .parts
-                        .unwrap()
-                        .into_iter()
-                        .map(|part| match part {
-                            Part::Text(text) => Some(text),
-                            _ => None,
-                        })
-                        .filter(Option::is_some)
-                        .flatten()
-                })
-            })
-            .collect::<String>();
+        let text = VertexClient::<T>::collect_text_from_response(response)?;
         Ok(Message::new(Role::Model, &text))
     }
 
@@ -143,33 +119,30 @@ impl<T: TokenProvider + Clone> VertexClient<T> {
             .stream_generate_content(&request, Model::GeminiPro)
             .await?;
 
-        // Check for errors in the response.
-        for chunk in &response {
-            if let Some(error) = &chunk.error {
-                tracing::error!("Error in response: {:?}", error);
-                let cloned = error.clone();
-                return Err(Error::VertexError(cloned));
+        VertexClient::<T>::collect_text_from_response(response)
+    }
+
+    fn collect_text_from_response(response: GenerateContentResponse) -> Result<String> {
+        let mut text = String::new();
+        for chunk in response {
+            match chunk {
+                ResponseStreamChunk::Ok(ok_response) => {
+                    for candidate in ok_response.candidates {
+                        if let Some(parts) = &candidate.content.parts {
+                            for part in parts {
+                                if let Part::Text(t) = part {
+                                    text.push_str(t);
+                                }
+                            }
+                        }
+                    }
+                }
+                ResponseStreamChunk::Error(err) => {
+                    tracing::error!("Error in response: {:?}", err);
+                    return Err(Error::VertexError(err.clone()));
+                }
             }
         }
-
-        let text = response
-            .into_iter()
-            .flat_map(|chunk| {
-                chunk.candidates.unwrap().into_iter().flat_map(|candidate| {
-                    candidate
-                        .content
-                        .parts
-                        .unwrap()
-                        .into_iter()
-                        .map(|part| match part {
-                            Part::Text(text) => Some(text),
-                            _ => None,
-                        })
-                        .filter(Option::is_some)
-                        .flatten()
-                })
-            })
-            .collect::<String>();
         Ok(text)
     }
 }