diff --git a/tracetools/CMakeLists.txt b/tracetools/CMakeLists.txt
index fa83f21..d1d3315 100644
--- a/tracetools/CMakeLists.txt
+++ b/tracetools/CMakeLists.txt
@@ -14,6 +14,7 @@ find_package(ament_cmake_ros REQUIRED)
 
 option(TRACETOOLS_DISABLED "Explicitly disable support for tracing with LTTng" OFF)
 if(NOT TRACETOOLS_DISABLED)
+  # Set TRACING_ENABLED if we can find lttng-ust
   find_package(PkgConfig)
   if(PkgConfig_FOUND)
     pkg_check_modules(LTTNG lttng-ust)
diff --git a/tracetools_test/CMakeLists.txt b/tracetools_test/CMakeLists.txt
index cb35969..24e3ffe 100644
--- a/tracetools_test/CMakeLists.txt
+++ b/tracetools_test/CMakeLists.txt
@@ -14,6 +14,7 @@ find_package(ament_cmake REQUIRED)
 
 option(TRACETOOLS_DISABLED "Explicitly disable support for tracing with LTTng" OFF)
 if(NOT TRACETOOLS_DISABLED)
+  # Set TRACING_ENABLED if we can find lttng-ust
   find_package(PkgConfig)
   if(PkgConfig_FOUND)
     pkg_check_modules(LTTNG lttng-ust)