diff --git a/src/Testcontainers/Clients/TestcontainersClient.cs b/src/Testcontainers/Clients/TestcontainersClient.cs
index e6852f95a..27c9188c7 100644
--- a/src/Testcontainers/Clients/TestcontainersClient.cs
+++ b/src/Testcontainers/Clients/TestcontainersClient.cs
@@ -339,7 +339,7 @@ public async Task<string> BuildAsync(IImageFromDockerfileConfiguration configura
         var cachedImages = await Image.GetAllAsync(filters, ct)
           .ConfigureAwait(false);
 
-        var repositoryTags = new HashSet<string>(cachedImages.SelectMany(image => image.RepoTags));
+        var repositoryTags = new HashSet<string>(cachedImages.SelectMany(image => image.RepoTags ?? Array.Empty<string>()));
 
         var uncachedImages = baseImages.Where(baseImage => !repositoryTags.Contains(baseImage.FullName));