diff --git a/apparmor.d/tunables/multiarch.d/system b/apparmor.d/tunables/multiarch.d/system
index d219c1d4..f2e7c256 100644
--- a/apparmor.d/tunables/multiarch.d/system
+++ b/apparmor.d/tunables/multiarch.d/system
@@ -55,8 +55,8 @@
 @{uuid}=@{h}@{h}@{h}@{h}@{h}@{h}@{h}@{h}[-_]@{h}@{h}@{h}@{h}[-_]@{h}@{h}@{h}@{h}[-_]@{h}@{h}@{h}@{h}[-_]@{h}@{h}@{h}@{h}@{h}@{h}@{h}@{h}@{h}@{h}@{h}@{h}
 
 # Username & group valid characters
-@{u}=[a-z0-9_]
-@{user}=[a-z_]{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}
+@{u}=[a-zA-Z0-9_]
+@{user}=[a-zA-Z_]{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}{@{u},}
 @{group}=@{user}
 
 # Shortcut for PCI device