diff --git a/docs/users_guide/runtime_control.rst b/docs/users_guide/runtime_control.rst
index f94c5846906dd0e33e31cfda874a83cf2287536f..2cf277176d5326957e8c45554114b8adcf95d846 100644
--- a/docs/users_guide/runtime_control.rst
+++ b/docs/users_guide/runtime_control.rst
@@ -1161,6 +1161,10 @@ When the program is linked with the :ghc-flag:`-eventlog` option
 
     - ``g`` — GC events, including GC start/stop. Enabled by default.
 
+    - ``n`` — non-moving garbage collector (see :rts-flag:`--nonmoving-gc`)
+      events including start and end of the concurrent mark and census
+      information to characterise heap fragmentation. Disabled by default.
+
     - ``p`` — parallel sparks (sampled). Enabled by default.
 
     - ``f`` — parallel sparks (fully accurate). Disabled by default.
diff --git a/rts/RtsFlags.c b/rts/RtsFlags.c
index 5b594c915d6bfb335e1b00f2b4564b5235496284..6180f42e396f43e6cf59fe509dd6ec317900a54e 100644
--- a/rts/RtsFlags.c
+++ b/rts/RtsFlags.c
@@ -382,6 +382,7 @@ usage_text[] = {
 "             where [flags] can contain:",
 "                s    scheduler events",
 "                g    GC and heap events",
+"                n    non-moving GC heap census events",
 "                p    par spark events (sampled)",
 "                f    par spark events (full detail)",
 "                u    user events (emitted from Haskell code)",
diff --git a/rts/sm/NonMoving.c b/rts/sm/NonMoving.c
index a39b889c92b4cc6c51e24120717df9b6556a606e..d230117b27a4be8846f47326e2969c8e38ef9596 100644
--- a/rts/sm/NonMoving.c
+++ b/rts/sm/NonMoving.c
@@ -1125,6 +1125,10 @@ static void nonmovingMark_(MarkQueue *mark_queue, StgWeak **dead_weaks, StgTSO *
     if (RtsFlags.DebugFlags.nonmoving_gc)
         nonmovingPrintAllocatorCensus();
 #endif
+#if defined(TRACING)
+    if (RtsFlags.TraceFlags.nonmoving_gc)
+        nonmovingTraceAllocatorCensus();
+#endif
 
     // TODO: Remainder of things done by GarbageCollect (update stats)