diff --git a/src/strutil.c b/src/strutil.c
index 62d2993e..f93e1151 100644
--- a/src/strutil.c
+++ b/src/strutil.c
@@ -591,7 +591,7 @@ const char *str_plural(int x) {
 static const char *str_filename(const char *fn, const char *stdname) {
   if(!fn)
     fn = "???";
-  char *p1 = strrchr(fn, '/'), *p2 = strrchr(fn, '\\');
+  const char *p1 = strrchr(fn, '/'), *p2 = strrchr(fn, '\\');
 
   return str_eq(fn, "-")? stdname: str_starts(fn, "/dev/")? fn: p1? p1 + 1: p2? p2 + 1: fn;
 }
diff --git a/src/usbasp.c b/src/usbasp.c
index b01d2711..049081a4 100644
--- a/src/usbasp.c
+++ b/src/usbasp.c
@@ -425,7 +425,7 @@ static int check_for_port_argument_match(const char *port, const char *bus,
 
   if(str_casestarts(port, "usb:")) {
     port += 4;
-    char *dev_name = strchr(port, ':');
+    const char *dev_name = strchr(port, ':');
 
     if(dev_name)                // Compare with busdir:devicefile
       return str_busdev_eq(port, bus) && str_busdev_eq(dev_name+1, device);
diff --git a/src/xbee.c b/src/xbee.c
index 82af30a6..0c88b9b0 100644
--- a/src/xbee.c
+++ b/src/xbee.c
@@ -968,7 +968,7 @@ static int xbeedev_open(const char *port, union pinfo pinfo, union filedescripto
    *
    * ... for a direct connection.
    */
-  char *ttySeparator = strchr(port, '@');
+  const char *ttySeparator = strchr(port, '@');
 
   if(ttySeparator == NULL) {
     pmsg_error("XBee: bad port syntax, require <xbee-address>@<serial-device>\n");
@@ -979,7 +979,7 @@ static int xbeedev_open(const char *port, union pinfo pinfo, union filedescripto
 
   XBeeBootSessionInit(xbs);
 
-  char *tty = &ttySeparator[1];
+  const char *tty = ttySeparator + 1;
 
   if(ttySeparator == port) {
     // Direct connection
@@ -1073,8 +1073,7 @@ static int xbeedev_open(const char *port, union pinfo pinfo, union filedescripto
   pmsg_notice("baud %ld\n", (long) pinfo.serialinfo.baud);
 
   {
-    const int rc = xbs->serialDevice->open(tty, pinfo,
-      &xbs->serialDescriptor);
+    const int rc = xbs->serialDevice->open(tty, pinfo, &xbs->serialDescriptor);
 
     if(rc < 0) {
       mmt_free(xbs);