diff --git a/litex/soc/cores/cpu/__init__.py b/litex/soc/cores/cpu/__init__.py
index 272007d0b..fdb3184e7 100644
--- a/litex/soc/cores/cpu/__init__.py
+++ b/litex/soc/cores/cpu/__init__.py
@@ -22,7 +22,7 @@ class CPU(Module):
 class CPUNone(CPU):
     data_width           = 32
     reset_address        = 0x00000000
-    io_regions           = {0x00000000: 0x1_0000_0000} # origin, length
+    io_regions           = {0x00000000: 0x100000000} # origin, length
 
 # CPUS ---------------------------------------------------------------------------------------------