diff --git a/qemu/scripts/decodetree.py b/qemu/scripts/decodetree.py
index 0db63419..4a63ba3e 100644
--- a/qemu/scripts/decodetree.py
+++ b/qemu/scripts/decodetree.py
@@ -723,7 +723,7 @@ def parse_generic(lineno, is_format, name, toks):
             continue
 
         # 'Foo=number' sets an argument field to a constant value
-        if re_fullmatch(re_ident + '=[0-9]+', t):
+        if re_fullmatch(re_ident + '=[+-]?[0-9]+', t):
             (fname, value) = t.split('=')
             value = int(value)
             flds = add_field(lineno, flds, fname, ConstField(value))