diff --git a/kernel/register.cc b/kernel/register.cc
index 47cfcde8b..fb0bc06d3 100644
--- a/kernel/register.cc
+++ b/kernel/register.cc
@@ -58,8 +58,8 @@ void try_collect_garbage()
 	if (!GarbageCollectionGuard::is_enabled() || !garbage_collection_requested)
 		return;
 	garbage_collection_requested = false;
-	for (auto &[idx, design] : *RTLIL::Design::get_all_designs())
-		design->gc_twines();
+	if (yosys_design)
+		yosys_design->gc_twines();
 }
 
 Pass::Pass(std::string name, std::string short_help, source_location location) :
diff --git a/kernel/register.h b/kernel/register.h
index 00310908b..42bafa7eb 100644
--- a/kernel/register.h
+++ b/kernel/register.h
@@ -46,7 +46,7 @@ public:
 // Call from anywhere to request GC at the next safe point.
 void request_garbage_collection();
 
-// GC if GarbageCollectionGuard::is_enabled() and GC was requested.
+// GC the active design if GarbageCollectionGuard::is_enabled() and GC was requested.
 void try_collect_garbage();
 
 struct Pass