diff --git a/scripts/base/frameworks/sumstats/plugins/topk.bro b/scripts/base/frameworks/sumstats/plugins/topk.bro
index 6107a252ae..a830b1c5ec 100644
--- a/scripts/base/frameworks/sumstats/plugins/topk.bro
+++ b/scripts/base/frameworks/sumstats/plugins/topk.bro
@@ -3,16 +3,27 @@
 module SumStats;
 
 export {
+	redef record Reducer += {
+		## number of elements to keep in the top-k list
+		topk_size: count &default=500;
+	};
+
 	redef enum Calculation += {
 		TOPK
 	};
 
 	redef record ResultVal += {
-		topk: opaque of topk &default=topk_init(500);
+		topk: opaque of topk &optional;
 	};
 
 }
 
+hook init_resultval_hook(r: Reducer, rv: ResultVal)
+	{
+	if ( TOPK in r$apply && ! rv?$topk )
+		rv$topk = topk_init(r$topk_size);
+	}
+
 hook observe_hook(r: Reducer, val: double, obs: Observation, rv: ResultVal)
 	{
 	if ( TOPK in r$apply ) 
@@ -24,7 +35,7 @@ hook observe_hook(r: Reducer, val: double, obs: Observation, rv: ResultVal)
 
 hook compose_resultvals_hook(result: ResultVal, rv1: ResultVal, rv2: ResultVal)
 	{
-	result$topk = topk_init(500);
+	result$topk = topk_init(topk_size(rv1$topk));
 
 	topk_merge(result$topk, rv1$topk);
 	topk_merge(result$topk, rv2$topk);
diff --git a/src/Topk.h b/src/Topk.h
index 30e87f7a99..51a2d75251 100644
--- a/src/Topk.h
+++ b/src/Topk.h
@@ -40,6 +40,7 @@ public:
 	VectorVal* getTopK(int k) const; // returns vector
 	uint64_t getCount(Val* value) const;
 	uint64_t getEpsilon(Val* value) const;
+	uint64_t getSize() const { return size; }
 	void Merge(const TopkVal* value);
 
 protected:
diff --git a/src/bro.bif b/src/bro.bif
index b6f101c025..4d0db54c8c 100644
--- a/src/bro.bif
+++ b/src/bro.bif
@@ -5684,6 +5684,13 @@ function topk_epsilon%(handle: opaque of topk, value: any%): count
 	return new Val(h->getEpsilon(value), TYPE_COUNT);
 	%}
 
+function topk_size%(handle: opaque of topk%): count
+	%{
+	assert(handle);
+	Topk::TopkVal* h = (Topk::TopkVal*) handle;
+	return new Val(h->getSize(), TYPE_COUNT);
+	%}
+
 function topk_merge%(handle1: opaque of topk, handle2: opaque of topk%): any
 	%{
 	assert(handle1);