diff --git a/Outputs/Speaker.hpp b/Outputs/Speaker.hpp
index 7d9215f50..4dee97da4 100644
--- a/Outputs/Speaker.hpp
+++ b/Outputs/Speaker.hpp
@@ -87,6 +87,7 @@ class Speaker {
 			Ensures any deferred processing occurs now.
 		*/
 		void flush() {
+			if(!queued_functions_) return;
 			std::shared_ptr<std::list<std::function<void(void)>>> queued_functions = queued_functions_;
 			queued_functions_.reset();
 			_queue->enqueue([queued_functions] {
@@ -143,7 +144,9 @@ template <class T> class Filter: public Speaker {
 
 		void run_for(const Cycles cycles) {
 			enqueue([=]() {
+				printf("... %d ...\n", (unsigned int)cycles.as_int());
 				unsigned int cycles_remaining = (unsigned int)cycles.as_int();
+				printf("!!!\n", (unsigned int)cycles.as_int());
 				if(coefficients_are_dirty_) update_filter_coefficients();
 
 				// if input and output rates exactly match, just accumulate results and pass on