diff --git a/src/kiss.c b/src/kiss.c
index 17902bf..89a0138 100644
--- a/src/kiss.c
+++ b/src/kiss.c
@@ -10,6 +10,10 @@ ssize_t patty_kiss_read(int fd, void *buf, size_t len, int *port) {
     int flags = KISS_NONE;
     size_t i, b = 0;
 
+    if (read(fd, buf, len) < 0) {
+        goto error_io;
+    }
+
     *port = 0;
 
     for (i=0; i<len; i++) {
@@ -25,10 +29,12 @@ ssize_t patty_kiss_read(int fd, void *buf, size_t len, int *port) {
 
         if (flags & KISS_ESCAPE) {
             if (c == PATTY_KISS_TFEND) {
-                ((char *)buf)[b++] = PATTY_KISS_FEND;
+                ((unsigned char *)buf)[b++] = PATTY_KISS_FEND;
             } else if (c == PATTY_KISS_TFESC) {
-                ((char *)buf)[b++] = PATTY_KISS_FESC;
+                ((unsigned char *)buf)[b++] = PATTY_KISS_FESC;
             } else {
+                errno = EIO;
+
                 goto error_io;
             }
 
@@ -60,7 +66,7 @@ ssize_t patty_kiss_read(int fd, void *buf, size_t len, int *port) {
                 continue;
             }
 
-            ((char *)buf)[b++] = c;
+            ((unsigned char *)buf)[b++] = c;
         }
     }