diff --git a/base/src/core/include/trace/subject_registry.h b/base/src/core/include/trace/subject_registry.h
index e548d2343..6ef3e263e 100644
--- a/base/src/core/include/trace/subject_registry.h
+++ b/base/src/core/include/trace/subject_registry.h
@@ -214,7 +214,7 @@ class Genode::Trace::Subject
 			/* inform trace source about the new buffer */
 			Locked_ptr<Source> source(_source);
 
-			if (!source.is_valid())
+			if (source.is_valid())
 				source->disable();
 		}