diff --git a/lib/kamal/configuration/validator/builder.rb b/lib/kamal/configuration/validator/builder.rb
index 8c8fe1f0..0115d437 100644
--- a/lib/kamal/configuration/validator/builder.rb
+++ b/lib/kamal/configuration/validator/builder.rb
@@ -8,6 +8,8 @@ class Kamal::Configuration::Validator::Builder < Kamal::Configuration::Validator
 
     error "Builder arch not set" unless config["arch"].present?
 
+    error "buildpacks only support building for one arch" if config["pack"] && config["arch"].is_a?(Array) && config["arch"].size > 1
+
     error "Cannot disable local builds, no remote is set" if config["local"] == false && config["remote"].blank?
   end
 end
diff --git a/test/configuration/validation_test.rb b/test/configuration/validation_test.rb
index 179aacfe..d16b2de2 100644
--- a/test/configuration/validation_test.rb
+++ b/test/configuration/validation_test.rb
@@ -94,6 +94,7 @@ class ConfigurationValidationTest < ActiveSupport::TestCase
     assert_error "builder/arch: should be an array or a string", builder: { "arch" => {} }
     assert_error "builder/args: should be a hash", builder: { "args" => [ "foo" ] }
     assert_error "builder/cache/options: should be a string", builder: { "cache" => { "options" => [] } }
+    assert_error "builder: buildpacks only support building for one arch", builder: { "arch" => [ "amd64", "arm64" ], "pack" => { "builder" => "heroku/builder:24" } }
   end
 
   private