1 files changed, 5 insertions, 1 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 63748c85d..baab74878 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -666,7 +666,6 @@ extern const char bb_default_login_shell[];
 #undef isascii
 #undef isblank
 #undef iscntrl
-#undef isdigit
 #undef isgraph
 #undef islower
 #undef isprint
@@ -675,6 +674,11 @@ extern const char bb_default_login_shell[];
 #undef isupper
 #undef isxdigit
 
+/* This one is more efficient - we save ~400 bytes */
+#undef isdigit
+#define isdigit(a) ((unsigned)((a) - '0') <= 9)
+
+
 #ifdef DMALLOC
 #include <dmalloc.h>
 #endif