diff --git a/qubesmgmt/utils.py b/qubesmgmt/utils.py
index 86db86b..06d065e 100644
--- a/qubesmgmt/utils.py
+++ b/qubesmgmt/utils.py
@@ -70,7 +70,7 @@ def parse_size(size):
         return int(size)
 
     for unit, multiplier in units:
-        if size.endswith(unit):
+        if size.endswith(unit.upper()):
             size = size[:-len(unit)].strip()
             return int(size) * multiplier