diff --git a/test/jitter/jitcore.py b/test/jitter/jitcore.py
index 1e009d9af..952458554 100644
--- a/test/jitter/jitcore.py
+++ b/test/jitter/jitcore.py
@@ -9,16 +9,16 @@
 jitter.cpu.RAX = 16565615892967251934
 assert jitter.cpu.RAX == 16565615892967251934
 
-jitter.cpu.RAX = -1
+jitter.cpu.RAX = -1 & 0xffffffffffffffff
 assert jitter.cpu.RAX == 0xffffffffffffffff
 
-jitter.cpu.RAX = -2
+jitter.cpu.RAX = -2 & 0xffffffffffffffff
 assert jitter.cpu.RAX == 0xfffffffffffffffe
 
-jitter.cpu.EAX = -2
+jitter.cpu.EAX = -2 & 0xffffffff
 assert jitter.cpu.EAX == 0xfffffffe
 
-jitter.cpu.RAX = -0xffffffffffffffff
+jitter.cpu.RAX = -0xffffffffffffffff & 0xffffffffffffffff
 assert jitter.cpu.RAX == 1
 
 try:
@@ -35,10 +35,10 @@
 else:
         raise Exception("Should see that 0x10000000000000000 is too big for RAX")
 
-jitter.cpu.EAX = -0xefffffff
+jitter.cpu.EAX = -0xefffffff & 0xffffffff
 assert jitter.cpu.EAX == 0x10000001
 
-jitter.cpu.EAX = -0xFFFFFFFF
+jitter.cpu.EAX = -0xFFFFFFFF & 0xffffffff
 assert jitter.cpu.EAX == 1
 
 try: