diff --git a/lib/sidekiq/extensions/generic_proxy.rb b/lib/sidekiq/extensions/generic_proxy.rb
index 313dd48c..139c420c 100644
--- a/lib/sidekiq/extensions/generic_proxy.rb
+++ b/lib/sidekiq/extensions/generic_proxy.rb
@@ -10,7 +10,7 @@ module Sidekiq
       def initialize(performable, target, options = {})
         @performable = performable
         @target = target
-        @opts = options
+        @opts = options.transform_keys(&:to_s)
       end
 
       def method_missing(name, *args)
diff --git a/lib/sidekiq/worker.rb b/lib/sidekiq/worker.rb
index 4e0140a8..b262bd16 100644
--- a/lib/sidekiq/worker.rb
+++ b/lib/sidekiq/worker.rb
@@ -175,16 +175,18 @@ module Sidekiq
 
       def initialize(klass, opts)
         @klass = klass
-        @opts = opts
+        # NB: the internal hash always has stringified keys
+        @opts = opts.transform_keys(&:to_s)
 
         # ActiveJob compatibility
-        interval = @opts.delete(:wait_until) || @opts.delete(:wait)
+        interval = @opts.delete("wait_until") || @opts.delete("wait")
         at(interval) if interval
       end
 
       def set(options)
-        interval = options.delete(:wait_until) || options.delete(:wait)
-        @opts.merge!(options)
+        hash = options.transform_keys(&:to_s)
+        interval = hash.delete("wait_until") || @opts.delete("wait")
+        @opts.merge!(hash)
         at(interval) if interval
         self
       end
@@ -200,7 +202,7 @@ module Sidekiq
       # Explicit inline execution of a job. Returns nil if the job did not
       # execute, true otherwise.
       def perform_inline(*args)
-        raw = @opts.merge("args" => args, "class" => @klass).transform_keys(&:to_s)
+        raw = @opts.merge("args" => args, "class" => @klass)
 
         # validate and normalize payload
         item = normalize_item(raw)
@@ -235,11 +237,10 @@ module Sidekiq
       alias_method :perform_sync, :perform_inline
 
       def perform_bulk(args, batch_size: 1_000)
-        hash = @opts.transform_keys(&:to_s)
         pool = Thread.current[:sidekiq_via_pool] || @klass.get_sidekiq_options["pool"] || Sidekiq.redis_pool
         client = Sidekiq::Client.new(pool)
         result = args.each_slice(batch_size).flat_map do |slice|
-          client.push_bulk(hash.merge("class" => @klass, "args" => slice))
+          client.push_bulk(@opts.merge("class" => @klass, "args" => slice))
         end
 
         result.is_a?(Enumerator::Lazy) ? result.force : result
@@ -353,9 +354,9 @@ module Sidekiq
 
       def client_push(item) # :nodoc:
         pool = Thread.current[:sidekiq_via_pool] || get_sidekiq_options["pool"] || Sidekiq.redis_pool
-        stringified_item = item.transform_keys(&:to_s)
+        raise ArgumentError, "Job payloads should contain no Symbols: #{item}" if item.any? { |k, v| k.is_a?(::Symbol) }
 
-        Sidekiq::Client.new(pool).push(stringified_item)
+        Sidekiq::Client.new(pool).push(item)
       end
     end
   end