1 files changed, 4 insertions, 3 deletions

diff --git a/src/lib/libc/net/ruserok.c b/src/lib/libc/net/ruserok.c
index 46fba4beb2..21646c156b 100644
--- a/src/lib/libc/net/ruserok.c
+++ b/src/lib/libc/net/ruserok.c
@@ -214,9 +214,10 @@ __ivaliduser_sa(FILE *hostf, struct sockaddr *raddr, socklen_t salen,
                 if (*p == '#')
                         continue;
                 while (p < buf + buflen && *p != '\n' && *p != ' ' && *p != '\t') {
-                        if (!isprint(*p))
+                        if (!isprint((unsigned char)*p))
                                 goto bail;
-                        *p = isupper(*p) ? tolower(*p) : *p;
+                        *p = isupper((unsigned char)*p) ?
+                            tolower((unsigned char)*p) : *p;
                         p++;
                 }
                 if (p >= buf + buflen)
@@ -230,7 +231,7 @@ __ivaliduser_sa(FILE *hostf, struct sockaddr *raddr, socklen_t salen,
                         user = p;
                         while (p < buf + buflen && *p != '\n' && *p != ' ' &&
                             *p != '\t') {
-                                if (!isprint(*p))
+                                if (!isprint((unsigned char)*p))
                                         goto bail;
                                 p++;
                         }