diff --git a/tools/marvin/marvin/lib/base.py b/tools/marvin/marvin/lib/base.py
index 82b82be7be3..6ca057c207b 100755
--- a/tools/marvin/marvin/lib/base.py
+++ b/tools/marvin/marvin/lib/base.py
@@ -626,7 +626,7 @@ class VirtualMachine:
         if custommemory:
             cmd.details[0]["memory"] = custommemory
 
-        if rootdisksize and rootdisksize >= 0:
+        if not rootdisksize is None and rootdisksize >= 0:
             cmd.details[0]["rootdisksize"] = rootdisksize
 
         if rootdiskcontroller: