diff --git a/src/sdeventplus/source/signal.hpp b/src/sdeventplus/source/signal.hpp
index 50bafa6..d5d9b5a 100644
--- a/src/sdeventplus/source/signal.hpp
+++ b/src/sdeventplus/source/signal.hpp
@@ -23,7 +23,8 @@
 
     /** @brief Creates a new signal event source on the provided event loop
      *         This type of source defaults to Enabled::On, executing the
-     *         callback for each signal observed.
+     *         callback for each signal observed. You are required to block
+     *         the signal in all threads prior to creating this source.
      *
      *  @param[in] event    - The event to attach the handler
      *  @param[in] sig      - Signum to watch, see signal(7)