diff --git a/repos/base-nova/src/core/platform.cc b/repos/base-nova/src/core/platform.cc
index 840dda9eb2..d9902b92c3 100644
--- a/repos/base-nova/src/core/platform.cc
+++ b/repos/base-nova/src/core/platform.cc
@@ -780,7 +780,7 @@ Platform::Platform() :
 		};
 
 		Idle_trace_source *source = new (core_mem_alloc())
-			Idle_trace_source(Affinity::Location(kernel_cpu_id, 0,
+			Idle_trace_source(Affinity::Location(genode_cpu_id, 0,
 			                                     _cpus.width(), 1),
 			                  sc_idle_base + kernel_cpu_id);