diff --git a/activestorage/lib/active_storage/attached/changes/create_one.rb b/activestorage/lib/active_storage/attached/changes/create_one.rb
index bb59a651ba..98aea36861 100644
--- a/activestorage/lib/active_storage/attached/changes/create_one.rb
+++ b/activestorage/lib/active_storage/attached/changes/create_one.rb
@@ -58,7 +58,7 @@ module ActiveStorage
         when String
           ActiveStorage::Blob.find_signed(attachable)
         else
-          raise "Could not find or build blob: expected attachable, got #{attachable.inspect}"
+          raise ArgumentError, "Could not find or build blob: expected attachable, got #{attachable.inspect}"
         end
       end
   end
diff --git a/activestorage/test/models/attached/many_test.rb b/activestorage/test/models/attached/many_test.rb
index ff2d29de11..bc44e9da68 100644
--- a/activestorage/test/models/attached/many_test.rb
+++ b/activestorage/test/models/attached/many_test.rb
@@ -253,7 +253,7 @@ class ActiveStorage::ManyAttachedTest < ActiveSupport::TestCase
   end
 
   test "creating a record with an unexpected object attached" do
-    error = assert_raises { User.create!(name: "Jason", highlights: :foo) }
+    error = assert_raises(ArgumentError) { User.create!(name: "Jason", highlights: :foo) }
     assert_equal "Could not find or build blob: expected attachable, got :foo", error.message
   end
 
diff --git a/activestorage/test/models/attached/one_test.rb b/activestorage/test/models/attached/one_test.rb
index af45b696ae..8654ecffef 100644
--- a/activestorage/test/models/attached/one_test.rb
+++ b/activestorage/test/models/attached/one_test.rb
@@ -255,7 +255,7 @@ class ActiveStorage::OneAttachedTest < ActiveSupport::TestCase
   end
 
   test "creating a record with an unexpected object attached" do
-    error = assert_raises { User.create!(name: "Jason", avatar: :foo) }
+    error = assert_raises(ArgumentError) { User.create!(name: "Jason", avatar: :foo) }
     assert_equal "Could not find or build blob: expected attachable, got :foo", error.message
   end