diff --git a/Lib/curses/ascii.py b/Lib/curses/ascii.py
index 6a466e0..5b243be 100644
--- a/Lib/curses/ascii.py
+++ b/Lib/curses/ascii.py
@@ -53,19 +53,19 @@
 
 def isalnum(c): return isalpha(c) or isdigit(c)
 def isalpha(c): return isupper(c) or islower(c)
-def isascii(c): return _ctoi(c) <= 127          # ?
+def isascii(c): return 0 <= _ctoi(c) <= 127          # ?
 def isblank(c): return _ctoi(c) in (9, 32)
-def iscntrl(c): return _ctoi(c) <= 31 or _ctoi(c) == 127
-def isdigit(c): return _ctoi(c) >= 48 and _ctoi(c) <= 57
-def isgraph(c): return _ctoi(c) >= 33 and _ctoi(c) <= 126
-def islower(c): return _ctoi(c) >= 97 and _ctoi(c) <= 122
-def isprint(c): return _ctoi(c) >= 32 and _ctoi(c) <= 126
+def iscntrl(c): return 0 <= _ctoi(c) <= 31 or _ctoi(c) == 127
+def isdigit(c): return 48 <= _ctoi(c) <= 57
+def isgraph(c): return 33 <= _ctoi(c) <= 126
+def islower(c): return 97 <= _ctoi(c) <= 122
+def isprint(c): return 32 <= _ctoi(c) <= 126
 def ispunct(c): return isgraph(c) and not isalnum(c)
 def isspace(c): return _ctoi(c) in (9, 10, 11, 12, 13, 32)
-def isupper(c): return _ctoi(c) >= 65 and _ctoi(c) <= 90
+def isupper(c): return 65 <= _ctoi(c) <= 90
 def isxdigit(c): return isdigit(c) or \
-    (_ctoi(c) >= 65 and _ctoi(c) <= 70) or (_ctoi(c) >= 97 and _ctoi(c) <= 102)
-def isctrl(c): return _ctoi(c) < 32
+    (65 <= _ctoi(c) <= 70) or (97 <= _ctoi(c) <= 102)
+def isctrl(c): return 0 <= _ctoi(c) < 32
 def ismeta(c): return _ctoi(c) > 127
 
 def ascii(c):