diff --git a/lib/isc/managers.c b/lib/isc/managers.c
index 094e4c0eb8..b57f8ab7c6 100644
--- a/lib/isc/managers.c
+++ b/lib/isc/managers.c
@@ -27,10 +27,13 @@ isc_managers_create(isc_mem_t *mctx, size_t workers, size_t quantum,
 	isc_timermgr_t *timermgr = NULL;
 
 	/*
-	 * We have ncpus network threads, ncpus old network threads - make
-	 * it 4x just to be on the safe side.
+	 * Currently, there are:
+	 * - 1 main thread
+	 * - 1 timer thread
+	 * - n netmgr threads
+	 * - n threadpool threads
 	 */
-	isc_hp_init(4 * workers);
+	isc_hp_init(2 + 2 * workers);
 
 	REQUIRE(netmgrp != NULL && *netmgrp == NULL);
 	isc__netmgr_create(mctx, workers, &netmgr);
diff --git a/lib/isc/tests/doh_test.c b/lib/isc/tests/doh_test.c
index 117728554d..7a2c06571b 100644
--- a/lib/isc/tests/doh_test.c
+++ b/lib/isc/tests/doh_test.c
@@ -27,6 +27,7 @@
 #include <isc/atomic.h>
 #include <isc/buffer.h>
 #include <isc/condition.h>
+#include <isc/hp.h>
 #include <isc/mutex.h>
 #include <isc/netmgr.h>
 #include <isc/nonce.h>
@@ -256,6 +257,8 @@ _setup(void **state) {
 		return (-1);
 	}
 
+	isc_hp_init(4 * workers);
+
 	signal(SIGPIPE, SIG_IGN);
 
 	return (0);