diff --git a/src/spy.c b/src/spy.c
index eb58f792a..0ca3050c2 100644
--- a/src/spy.c
+++ b/src/spy.c
@@ -229,7 +229,7 @@ int setstealth_cmd(unit * u, struct order *ord)
         return 0;
     }
 
-    if (isdigit(s[0])) {
+    if (isdigit(*(const unsigned char *)s)) {
         /* Tarnungslevel setzen */
         level = atoi((const char *)s);
         if (level > effskill(u, SK_STEALTH, 0)) {
diff --git a/src/util/base36.c b/src/util/base36.c
index 7edb46027..285e9760e 100644
--- a/src/util/base36.c
+++ b/src/util/base36.c
@@ -39,9 +39,9 @@ int atoi36(const char *str)
     while (isalnum(*(unsigned char *)s)) {
         if (isupper(*(unsigned char *)s))
             i = i * 36 + (*s) - 'A' + 10;
-        else if (islower(*(unsigned char *)s))
+        else if (islower(*s))
             i = i * 36 + (*s) - 'a' + 10;
-        else if (isdigit(*(unsigned char *)s))
+        else if (isdigit(*s))
             i = i * 36 + (*s) - '0';
         else
             break;
diff --git a/src/util/dice.c b/src/util/dice.c
index e28a4bccd..6fa50261d 100644
--- a/src/util/dice.c
+++ b/src/util/dice.c
@@ -49,7 +49,7 @@ static int term_eval(const char **sptr)
     int state = 1;
 
     for (;;) {
-        if (isdigit(*(unsigned char *)c)) {
+        if (isdigit(*(const unsigned char *)c)) {
             k = k * 10 + (*c - '0');
         }
         else if (*c == '+' || *c == '-' || *c == 0 || *c == '*' || *c == ')'
diff --git a/src/util/parser.c b/src/util/parser.c
index bbdb5ac7e..fca066cb1 100644
--- a/src/util/parser.c
+++ b/src/util/parser.c
@@ -6,7 +6,6 @@
 
 #include <assert.h>
 #include <stdlib.h>
-#include <ctype.h>
 #include <wctype.h>
 #include <memory.h>
 
@@ -251,7 +250,8 @@ unsigned int atoip(const char *s)
     int n;
 
     assert(s);
-    n = isdigit(s[0]) ? atoi(s) : 0;
+    n = (s[0] >='0' && s[0]<='9');
+    n = n ? atoi(s) : 0;
 
     if (n < 0)
         n = 0;
diff --git a/src/util/translation.c b/src/util/translation.c
index c733cc272..fb89a5af9 100644
--- a/src/util/translation.c
+++ b/src/util/translation.c
@@ -354,7 +354,7 @@ static const char *parse(opstack ** stack, const char *inn,
             return parse_symbol(stack, ++b, userdata);
             break;
         default:
-            if (isdigit(*(unsigned char *)b) || *b == '-' || *b == '+') {
+            if (isdigit(*(const unsigned char *)b) || *b == '-' || *b == '+') {
                 return parse_int(stack, b);
             }
             else