diff --git a/src/ax25.c b/src/ax25.c
index ac9a5b8..f453244 100644
--- a/src/ax25.c
+++ b/src/ax25.c
@@ -38,10 +38,10 @@ int patty_ax25_pton(const char *callsign,
                     goto error_invalid_callsign;
                 }
 
-                if ((c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z')) {
-                    addr->callsign[o++] = (c & 0x7f) << 1;
-                } else if (c == '-') {
+                if (c == '-') {
                     state = ADDR_SSID;
+                } else if (PATTY_AX25_ADDR_CHAR_VALID(c)) {
+                    addr->callsign[o++] = (c & 0x7f) << 1;
                 } else {
                     goto error_invalid_callsign;
                 }