diff --git a/Storage/src/commonMain/kotlin/io/github/jan/supabase/storage/BucketApi.kt b/Storage/src/commonMain/kotlin/io/github/jan/supabase/storage/BucketApi.kt
index aa164c97..5c76d495 100644
--- a/Storage/src/commonMain/kotlin/io/github/jan/supabase/storage/BucketApi.kt
+++ b/Storage/src/commonMain/kotlin/io/github/jan/supabase/storage/BucketApi.kt
@@ -34,36 +34,33 @@ sealed interface BucketApi {
      * Uploads a file in [bucketId] under [path]
      * @param path The path to upload the file to
      * @param data The data to upload
-     * @param upsert Whether to overwrite an existing file
      * @return the key to the uploaded file
      * @throws IllegalArgumentException if data to upload is empty
      * @throws RestException or one of its subclasses if receiving an error response
      * @throws HttpRequestTimeoutException if the request timed out
      * @throws HttpRequestException on network related issues
      */
-    suspend fun upload(path: String, data: ByteArray, upsert: Boolean = false, options: FileOptionBuilder.() -> Unit = {}): FileUploadResponse {
+    suspend fun upload(path: String, data: ByteArray, options: FileOptionBuilder.() -> Unit = {}): FileUploadResponse {
         require(data.isNotEmpty()) { "The data to upload should not be empty" }
-        return upload(path, UploadData(ByteReadChannel(data), data.size.toLong()), upsert, options)
+        return upload(path, UploadData(ByteReadChannel(data), data.size.toLong()), options)
     }
 
     /**
      * Uploads a file in [bucketId] under [path]
      * @param path The path to upload the file to
      * @param data The data to upload
-     * @param upsert Whether to overwrite an existing file
      * @return the key to the uploaded file
      * @throws RestException or one of its subclasses if receiving an error response
      * @throws HttpRequestTimeoutException if the request timed out
      * @throws HttpRequestException on network related issues
      */
-    suspend fun upload(path: String, data: UploadData, upsert: Boolean = false, options: FileOptionBuilder.() -> Unit = {}): FileUploadResponse
+    suspend fun upload(path: String, data: UploadData, options: FileOptionBuilder.() -> Unit = {}): FileUploadResponse
 
     /**
      * Uploads a file in [bucketId] under [path] using a presigned url
      * @param path The path to upload the file to
-     * @param token The presigned url token
+     * @param token The pre-signed url token
      * @param data The data to upload
-     * @param upsert Whether to overwrite an existing file
      * @return the key of the uploaded file
      * @throws IllegalArgumentException if data to upload is empty
      */
@@ -71,11 +68,10 @@ sealed interface BucketApi {
         path: String,
         token: String,
         data: ByteArray,
-        upsert: Boolean = false,
         options: FileOptionBuilder.() -> Unit = {}
     ): FileUploadResponse {
         require(data.isNotEmpty()) { "The data to upload should not be empty" }
-        return uploadToSignedUrl(path, token, UploadData(ByteReadChannel(data), data.size.toLong()), upsert, options)
+        return uploadToSignedUrl(path, token, UploadData(ByteReadChannel(data), data.size.toLong()), options)
     }
 
     /**
@@ -83,42 +79,39 @@ sealed interface BucketApi {
      * @param path The path to upload the file to
      * @param token The presigned url token
      * @param data The data to upload
-     * @param upsert Whether to overwrite an existing file
      * @return the key of the uploaded file
      * @throws RestException or one of its subclasses if receiving an error response
      * @throws HttpRequestTimeoutException if the request timed out
      * @throws HttpRequestException on network related issues
      * @throws HttpRequestException on network related issues
      */
-    suspend fun uploadToSignedUrl(path: String, token: String, data: UploadData, upsert: Boolean = false, options: FileOptionBuilder.() -> Unit = {}): FileUploadResponse
+    suspend fun uploadToSignedUrl(path: String, token: String, data: UploadData, options: FileOptionBuilder.() -> Unit = {}): FileUploadResponse
 
     /**
      * Updates a file in [bucketId] under [path]
      * @param path The path to update the file to
      * @param data The new data
-     * @param upsert Whether to overwrite an existing file
      * @return the key to the updated file
      * @throws IllegalArgumentException if data to upload is empty
      * @throws RestException or one of its subclasses if receiving an error response
      * @throws HttpRequestTimeoutException if the request timed out
      * @throws HttpRequestException on network related issues
      */
-    suspend fun update(path: String, data: ByteArray, upsert: Boolean = false, options: FileOptionBuilder.() -> Unit = {}): FileUploadResponse {
+    suspend fun update(path: String, data: ByteArray, options: FileOptionBuilder.() -> Unit = {}): FileUploadResponse {
         require(data.isNotEmpty()) { "The data to upload should not be empty" }
-        return update(path, UploadData(ByteReadChannel(data), data.size.toLong()), upsert, options)
+        return update(path, UploadData(ByteReadChannel(data), data.size.toLong()), options)
     }
 
     /**
      * Updates a file in [bucketId] under [path]
      * @param path The path to update the file to
      * @param data The new data
-     * @param upsert Whether to overwrite an existing file
      * @return the key to the updated file
      * @throws RestException or one of its subclasses if receiving an error response
      * @throws HttpRequestTimeoutException if the request timed out
      * @throws HttpRequestException on network related issues
      */
-    suspend fun update(path: String, data: UploadData, upsert: Boolean = false, options: FileOptionBuilder.() -> Unit = {}): FileUploadResponse
+    suspend fun update(path: String, data: UploadData, options: FileOptionBuilder.() -> Unit = {}): FileUploadResponse
 
     /**
      * Deletes all files in [bucketId] with in [paths]
diff --git a/Storage/src/commonMain/kotlin/io/github/jan/supabase/storage/BucketApiImpl.kt b/Storage/src/commonMain/kotlin/io/github/jan/supabase/storage/BucketApiImpl.kt
index 6051ccf3..76c83d16 100644
--- a/Storage/src/commonMain/kotlin/io/github/jan/supabase/storage/BucketApiImpl.kt
+++ b/Storage/src/commonMain/kotlin/io/github/jan/supabase/storage/BucketApiImpl.kt
@@ -44,21 +44,19 @@ internal class BucketApiImpl(override val bucketId: String, val storage: Storage
     override suspend fun update(
         path: String,
         data: UploadData,
-        upsert: Boolean,
         options: FileOptionBuilder.() -> Unit
     ): FileUploadResponse =
         uploadOrUpdate(
-            HttpMethod.Put, bucketId, path, data, upsert, options
+            HttpMethod.Put, bucketId, path, data, options
         )
 
     override suspend fun uploadToSignedUrl(
         path: String,
         token: String,
         data: UploadData,
-        upsert: Boolean,
         options: FileOptionBuilder.() -> Unit
     ): FileUploadResponse {
-        return uploadToSignedUrl(path, token, data, upsert, options) {}
+        return uploadToSignedUrl(path, token, data, options) {}
     }
 
     override suspend fun createSignedUploadUrl(path: String): UploadSignedUrl {
@@ -77,11 +75,10 @@ internal class BucketApiImpl(override val bucketId: String, val storage: Storage
     override suspend fun upload(
         path: String,
         data: UploadData,
-        upsert: Boolean,
         options: FileOptionBuilder.() -> Unit
     ): FileUploadResponse =
         uploadOrUpdate(
-            HttpMethod.Post, bucketId, path, data, upsert, options
+            HttpMethod.Post, bucketId, path, data, options
         )
 
     override suspend fun delete(paths: Collection<String>) {
@@ -249,14 +246,13 @@ internal class BucketApiImpl(override val bucketId: String, val storage: Storage
         bucket: String,
         path: String,
         data: UploadData,
-        upsert: Boolean,
         options: FileOptionBuilder.() -> Unit,
         extra: HttpRequestBuilder.() -> Unit = {}
     ): FileUploadResponse {
         val optionBuilder = FileOptionBuilder(storage.serializer).apply(options)
         val response = storage.api.request("object/$bucket/$path") {
             this.method = method
-            defaultUploadRequest(path, data, upsert, optionBuilder, extra)
+            defaultUploadRequest(path, data, optionBuilder, extra)
         }.body<JsonObject>()
         val key = response["Key"]?.jsonPrimitive?.content
             ?: error("Expected a key in a upload response")
@@ -271,14 +267,13 @@ internal class BucketApiImpl(override val bucketId: String, val storage: Storage
         path: String,
         token: String,
         data: UploadData,
-        upsert: Boolean,
         options: FileOptionBuilder.() -> Unit,
         extra: HttpRequestBuilder.() -> Unit = {}
     ): FileUploadResponse {
         val optionBuilder = FileOptionBuilder(storage.serializer).apply(options)
         val response = storage.api.put("object/upload/sign/$bucketId/$path") {
             parameter("token", token)
-            defaultUploadRequest(path, data, upsert, optionBuilder, extra)
+            defaultUploadRequest(path, data, optionBuilder, extra)
         }.body<JsonObject>()
         val key = response["Key"]?.jsonPrimitive?.content
             ?: error("Expected a key in a upload response")
@@ -291,17 +286,16 @@ internal class BucketApiImpl(override val bucketId: String, val storage: Storage
     private fun HttpRequestBuilder.defaultUploadRequest(
         path: String,
         data: UploadData,
-        upsert: Boolean,
         optionBuilder: FileOptionBuilder,
         extra: HttpRequestBuilder.() -> Unit
     ) {
         setBody(object : OutgoingContent.ReadChannelContent() {
-            override val contentType: ContentType = ContentType.defaultForFilePath(path)
+            override val contentType: ContentType = optionBuilder.contentType ?: ContentType.defaultForFilePath(path)
             override val contentLength: Long = data.size
             override fun readFrom(): ByteReadChannel = data.stream
         })
-        header(HttpHeaders.ContentType, ContentType.defaultForFilePath(path))
-        header(UPSERT_HEADER, upsert.toString())
+        header(HttpHeaders.ContentType, optionBuilder.contentType ?: ContentType.defaultForFilePath(path))
+        header(UPSERT_HEADER, optionBuilder.upsert.toString())
         optionBuilder.userMetadata?.let {
             header("x-metadata", Base64.Default.encode(it.toString().encodeToByteArray()).also((::println)))
         }
diff --git a/Storage/src/commonMain/kotlin/io/github/jan/supabase/storage/FileOptionBuilder.kt b/Storage/src/commonMain/kotlin/io/github/jan/supabase/storage/FileOptionBuilder.kt
index d59c30e5..67b998ca 100644
--- a/Storage/src/commonMain/kotlin/io/github/jan/supabase/storage/FileOptionBuilder.kt
+++ b/Storage/src/commonMain/kotlin/io/github/jan/supabase/storage/FileOptionBuilder.kt
@@ -2,6 +2,7 @@ package io.github.jan.supabase.storage
 
 import io.github.jan.supabase.SupabaseSerializer
 import io.github.jan.supabase.encodeToJsonElement
+import io.ktor.http.ContentType
 import kotlinx.serialization.json.JsonObject
 import kotlinx.serialization.json.JsonObjectBuilder
 import kotlinx.serialization.json.buildJsonObject
@@ -11,10 +12,14 @@ import kotlinx.serialization.json.jsonObject
  * Builder for uploading files with additional options
  * @param serializer The serializer to use for encoding the metadata
  * @param userMetadata The user metadata to upload with the file
+ * @param upsert Whether to update the file if it already exists
+ * @param contentType The content type of the file. If null, the content type will be inferred from the file extension
  */
 class FileOptionBuilder(
     @PublishedApi internal val serializer: SupabaseSerializer,
     var userMetadata: JsonObject? = null,
+    var upsert: Boolean = false,
+    var contentType: ContentType? = null,
 ) {
 
     /**
diff --git a/Storage/src/commonTest/kotlin/BucketApiTest.kt b/Storage/src/commonTest/kotlin/BucketApiTest.kt
index 2dc3640c..ac09886a 100644
--- a/Storage/src/commonTest/kotlin/BucketApiTest.kt
+++ b/Storage/src/commonTest/kotlin/BucketApiTest.kt
@@ -89,8 +89,9 @@ class BucketApiTest {
                 )
             },
             request = { client, expectedPath, data, meta ->
-                client.storage[bucketId].upload(expectedPath, data, upsert = true) {
+                client.storage[bucketId].upload(expectedPath, data) {
                     userMetadata = meta
+                    upsert = true
                 }
             }
         )
@@ -115,8 +116,9 @@ class BucketApiTest {
                 )
             },
             request = { client, expectedPath, data, meta ->
-                client.storage[bucketId].uploadToSignedUrl(path = expectedPath, token = expectedToken, data = data, upsert = false) {
+                client.storage[bucketId].uploadToSignedUrl(path = expectedPath, token = expectedToken, data = data) {
                     userMetadata = meta
+                    upsert = false
                 }
             }
         )
@@ -141,8 +143,9 @@ class BucketApiTest {
                 )
             },
             request = { client, expectedPath, data, meta ->
-                client.storage[bucketId].uploadToSignedUrl(path = expectedPath, token = expectedToken, data = data, upsert = true) {
+                client.storage[bucketId].uploadToSignedUrl(path = expectedPath, token = expectedToken, data = data) {
                     userMetadata = meta
+                    upsert = true
                 }
             }
         )
@@ -181,8 +184,9 @@ class BucketApiTest {
                 )
             },
             request = { client, expectedPath, data, meta ->
-                client.storage[bucketId].update(expectedPath, data, upsert = true) {
+                client.storage[bucketId].update(expectedPath, data) {
                     userMetadata = meta
+                    upsert = true
                 }
             }
         )