diff --git a/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/DataSourceExtensions.kt b/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/DataSourceExtensions.kt
index 6a10001..4b7f291 100644
--- a/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/DataSourceExtensions.kt
+++ b/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/DataSourceExtensions.kt
@@ -1,6 +1,10 @@
 package gq.kirmanak.mealient.datasource
 
 import kotlinx.coroutines.CancellationException
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.decodeFromStream
+import okhttp3.ResponseBody
 
 /**
  * Like [runCatching] but rethrows [CancellationException] to support
@@ -13,3 +17,6 @@ inline fun <T> runCatchingExceptCancel(block: () -> T): Result<T> = try {
 } catch (e: Throwable) {
     Result.failure(e)
 }
+
+@OptIn(ExperimentalSerializationApi::class)
+inline fun <reified R> ResponseBody.decode(json: Json): R = json.decodeFromStream(byteStream())
diff --git a/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/v0/MealieDataSourceV0Impl.kt b/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/v0/MealieDataSourceV0Impl.kt
index d8fd7b8..641fb12 100644
--- a/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/v0/MealieDataSourceV0Impl.kt
+++ b/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/v0/MealieDataSourceV0Impl.kt
@@ -2,13 +2,11 @@ package gq.kirmanak.mealient.datasource.v0
 
 import gq.kirmanak.mealient.datasource.NetworkError
 import gq.kirmanak.mealient.datasource.NetworkRequestWrapper
+import gq.kirmanak.mealient.datasource.decode
 import gq.kirmanak.mealient.datasource.v0.models.*
 import gq.kirmanak.mealient.logging.Logger
-import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.SerializationException
 import kotlinx.serialization.json.Json
-import kotlinx.serialization.json.decodeFromStream
-import okhttp3.ResponseBody
 import retrofit2.HttpException
 import java.net.ConnectException
 import java.net.SocketTimeoutException
@@ -43,7 +41,7 @@ class MealieDataSourceV0Impl @Inject constructor(
         logParameters = { "baseUrl = $baseUrl, username = $username, password = $password" }
     ).map { it.accessToken }.getOrElse {
         val errorBody = (it as? HttpException)?.response()?.errorBody() ?: throw it
-        val errorDetailV0 = errorBody.decode<ErrorDetailV0>()
+        val errorDetailV0 = errorBody.decode<ErrorDetailV0>(json)
         throw if (errorDetailV0.detail == "Unauthorized") NetworkError.Unauthorized(it) else it
     }
 
@@ -81,7 +79,4 @@ class MealieDataSourceV0Impl @Inject constructor(
         logMethod = { "requestRecipeInfo" },
         logParameters = { "baseUrl = $baseUrl, token = $token, slug = $slug" }
     )
-
-    @OptIn(ExperimentalSerializationApi::class)
-    private inline fun <reified R> ResponseBody.decode(): R = json.decodeFromStream(byteStream())
 }
diff --git a/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/v1/MealieDataSourceV1Impl.kt b/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/v1/MealieDataSourceV1Impl.kt
index 965e1f7..0857a91 100644
--- a/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/v1/MealieDataSourceV1Impl.kt
+++ b/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/v1/MealieDataSourceV1Impl.kt
@@ -2,7 +2,9 @@ package gq.kirmanak.mealient.datasource.v1
 
 import gq.kirmanak.mealient.datasource.NetworkError
 import gq.kirmanak.mealient.datasource.NetworkRequestWrapper
+import gq.kirmanak.mealient.datasource.decode
 import gq.kirmanak.mealient.datasource.v0.models.AddRecipeRequestV0
+import gq.kirmanak.mealient.datasource.v1.models.ErrorDetailV1
 import gq.kirmanak.mealient.datasource.v1.models.GetRecipeResponseV1
 import gq.kirmanak.mealient.datasource.v1.models.GetRecipeSummaryResponseV1
 import gq.kirmanak.mealient.datasource.v1.models.VersionResponseV1
@@ -29,8 +31,18 @@ class MealieDataSourceV1Impl @Inject constructor(
         TODO("Not yet implemented")
     }
 
-    override suspend fun authenticate(baseUrl: String, username: String, password: String): String {
-        TODO("Not yet implemented")
+    override suspend fun authenticate(
+        baseUrl: String,
+        username: String,
+        password: String,
+    ): String = networkRequestWrapper.makeCall(
+        block = { service.getToken("$baseUrl/api/auth/token", username, password) },
+        logMethod = { "authenticate" },
+        logParameters = { "baseUrl = $baseUrl, username = $username, password = $password" }
+    ).map { it.accessToken }.getOrElse {
+        val errorBody = (it as? HttpException)?.response()?.errorBody() ?: throw it
+        val errorDetailV0 = errorBody.decode<ErrorDetailV1>(json)
+        throw if (errorDetailV0.detail == "Unauthorized") NetworkError.Unauthorized(it) else it
     }
 
     override suspend fun getVersionInfo(
diff --git a/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/v1/models/ErrorDetailV1.kt b/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/v1/models/ErrorDetailV1.kt
new file mode 100644
index 0000000..b3f1810
--- /dev/null
+++ b/datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/v1/models/ErrorDetailV1.kt
@@ -0,0 +1,7 @@
+package gq.kirmanak.mealient.datasource.v1.models
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class ErrorDetailV1(@SerialName("detail") val detail: String? = null)
\ No newline at end of file