diff --git a/tests/libtest/isc.c b/tests/libtest/isc.c
index b0f12576f2..1604d66ee4 100644
--- a/tests/libtest/isc.c
+++ b/tests/libtest/isc.c
@@ -17,6 +17,7 @@
 #include <signal.h>
 #include <stdbool.h>
 #include <stdlib.h>
+#include <sys/resource.h>
 #include <time.h>
 
 #include <isc/buffer.h>
@@ -40,6 +41,18 @@ isc_taskmgr_t *taskmgr = NULL;
 isc_nm_t *netmgr = NULL;
 unsigned int workers = -1;
 
+static void
+adjustnofile(void) {
+	struct rlimit rl;
+
+	if (getrlimit(RLIMIT_NOFILE, &rl) == 0) {
+		if (rl.rlim_cur != rl.rlim_max) {
+			rl.rlim_cur = rl.rlim_max;
+			setrlimit(RLIMIT_NOFILE, &rl);
+		}
+	}
+}
+
 int
 setup_mctx(void **state __attribute__((__unused__))) {
 	isc_mem_debugging |= ISC_MEM_DEBUGRECORD;
@@ -107,6 +120,8 @@ int
 setup_netmgr(void **state __attribute__((__unused__))) {
 	REQUIRE(loopmgr != NULL);
 
+	adjustnofile();
+
 	isc_netmgr_create(mctx, loopmgr, &netmgr);
 
 	return (0);