diff --git a/toys/posix/find.c b/toys/posix/find.c
index ac1488161..3dea5fb27 100644
--- a/toys/posix/find.c
+++ b/toys/posix/find.c
@@ -421,7 +421,7 @@ static int do_find(struct dirtree *new)
           test = *arg;
         }
 
-      } else if (strchr("acm", *s)
+      } else if (stridx("acm", *s) != -1
         && (!strcmp(s+1, "time") || !strcmp(s+1, "min")))
       {
         if (check) {
diff --git a/toys/posix/printf.c b/toys/posix/printf.c
index c80e6fe40..08f860a3f 100644
--- a/toys/posix/printf.c
+++ b/toys/posix/printf.c
@@ -97,7 +97,7 @@ void printf_main(void)
 
         // Parse width.precision between % and type indicator.
         *to++ = '%';
-        while (strchr("-+# '0", *f) && (to-toybuf)<10) *to++ = *f++;
+        while (stridx("-+# '0", *f) != -1 && (to-toybuf)<10) *to++ = *f++;
         for (;;) {
           if (chrstart(&f, '*')) {
             if (*arg) wp[i] = atolx(*arg++);
@@ -118,7 +118,7 @@ void printf_main(void)
           continue;
         } else if (c == 'c') printf(toybuf, wp[0], wp[1], *aa);
         else if (c == 's') printf(toybuf, wp[0], wp[1], aa);
-        else if (strchr("diouxX", c)) {
+        else if (stridx("diouxX", c) != -1) {
           long long ll;
 
           if (*aa == '\'' || *aa == '"') ll = aa[1];
@@ -126,7 +126,7 @@ void printf_main(void)
 
           sprintf(to, "*.*ll%c", c);
           printf(toybuf, wp[0], wp[1], ll);
-        } else if (strchr("feEgG", c)) {
+        } else if (stridx("feEgG", c) != -1) {
           long double ld = strtold(aa, &end);
 
           sprintf(to, "*.*L%c", c);
diff --git a/toys/posix/sed.c b/toys/posix/sed.c
index 085884957..9fa545eac 100644
--- a/toys/posix/sed.c
+++ b/toys/posix/sed.c
@@ -719,7 +719,7 @@ static char *unescape_delimited_string(char **pstr, char *delim)
       if (!mode) {
         mode = ']';
         if (from[1]=='-' || from[1]==']') *(to++) = *(from++);
-      } else if (mode == ']' && strchr(".=:", from[1])) {
+      } else if (mode == ']' && stridx(".=:", from[1]) != -1) {
         *(to++) = *(from++);
         mode = *from;
       }