diff --git a/libraries/AP_AIS/AP_AIS.cpp b/libraries/AP_AIS/AP_AIS.cpp
index 29bde18a8b..621dd84fe2 100644
--- a/libraries/AP_AIS/AP_AIS.cpp
+++ b/libraries/AP_AIS/AP_AIS.cpp
@@ -804,15 +804,4 @@ bool AP_AIS::decode_latest_term()
     return false;
 }
 
-// return the numeric value of an ascii hex character
-int16_t AP_AIS::char_to_hex(char a)
-{
-    if (a >= 'A' && a <= 'F')
-        return a - 'A' + 10;
-    else if (a >= 'a' && a <= 'f')
-        return a - 'a' + 10;
-    else
-        return a - '0';
-}
-
 #endif  // HAL_AIS_ENABLED
diff --git a/libraries/AP_AIS/AP_AIS.h b/libraries/AP_AIS/AP_AIS.h
index a31a187988..e7507f35bf 100644
--- a/libraries/AP_AIS/AP_AIS.h
+++ b/libraries/AP_AIS/AP_AIS.h
@@ -123,9 +123,6 @@ private:
     // decode each term
     bool decode_latest_term() WARN_IF_UNUSED;
 
-    // convert from char to hex value for checksum
-    int16_t char_to_hex(char a);
-
     // varables for decoding NMEA sentence
     char _term[AIVDM_PAYLOAD_SIZE]; // buffer for the current term within the current sentence
     uint8_t _term_offset;           // offset within the _term buffer where the next character should be placed