diff --git a/libtransmission/clients.c b/libtransmission/clients.c
index a5891aaec..bb6c154e8 100644
--- a/libtransmission/clients.c
+++ b/libtransmission/clients.c
@@ -36,9 +36,9 @@
 static int
 charint( char ch )
 {
-    if( isdigit( ch ) ) return ch - '0';
-    if( isupper( ch ) ) return 10 + ch - 'A';
-    if( islower( ch ) ) return 36 + ch - 'a';
+    if( '0' <= ch && ch <= '9' ) return      ch - '0';
+    if( 'A' <= ch && ch <= 'Z' ) return 10 + ch - 'A';
+    if( 'a' <= ch && ch <= 'z' ) return 36 + ch - 'a';
     return 0;
 }
 
diff --git a/libtransmission/tracker.c b/libtransmission/tracker.c
index c49032ec6..aa925f295 100644
--- a/libtransmission/tracker.c
+++ b/libtransmission/tracker.c
@@ -841,9 +841,9 @@ generateKeyParam( char * msg, int len )
 static int
 is_rfc2396_alnum( char ch )
 {
-    return ( (ch >= 'a' && ch <= 'z' )
-            || (ch >= 'A' && ch <= 'Z' )
-            || (ch >= '0' && ch <= '9' ) );
+    return     ( '0' <= ch && ch <= '9' )
+            || ( 'A' <= ch && ch <= 'Z' )
+            || ( 'a' <= ch && ch <= 'z' );
 }
 
 static void