diff --git a/tools/runner.py b/tools/runner.py
index 03f44611..e50ba9c0 100644
--- a/tools/runner.py
+++ b/tools/runner.py
@@ -552,7 +552,12 @@ class UmlRunner(RunnerAbstract):
 
 		kern_log = "ignore_loglevel" if "kernel" in args.verbose else "quiet"
 
-		cmd = [args.kernel, 'rootfstype=hostfs', 'ro', 'mem=256M', 'mac80211_hwsim.radios=0',
+		if self.args.valgrind:
+			ram = 512
+		else:
+			ram = 256
+
+		cmd = [args.kernel, 'rootfstype=hostfs', 'ro', f'mem={ram}M', 'mac80211_hwsim.radios=0',
 				'time-travel=inf-cpu', 'eth0=mcast', 'eth1=mcast',
 				'%s' % kern_log, 'init=%s' % self.init]
 		cmd.extend(args.to_cmd().split(' '))