diff --git a/platformio.ini b/platformio.ini
index c7954e7a..52456ffc 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -11,10 +11,10 @@ monitor_filters = esp32_exception_decoder, log2file
 build_flags = 
   -Wall -Wextra -Wunused -Wmisleading-indentation -Wduplicated-cond -Wlogical-op -Wnull-dereference
   ; -D TINY_GSM_MODEM_SIM7000
-  -D TINY_GSM_MODEM_SIM7020
+  ; -D TINY_GSM_MODEM_SIM7020
   ; -D TINY_GSM_MODEM_SIM7600
   ; -D TINY_GSM_MODEM_A7608
-  ; -D TINY_GSM_MODEM_A7670
+  -D TINY_GSM_MODEM_A7670
   ; -D TINY_GSM_MODEM_SIM7672
 
 [env:esp32dev]
diff --git a/src/TinyGsmHttpsA76xx.h b/src/TinyGsmHttpsA76xx.h
index 3f44c8ba..a10ea3b9 100644
--- a/src/TinyGsmHttpsA76xx.h
+++ b/src/TinyGsmHttpsA76xx.h
@@ -278,21 +278,19 @@ class TinyGsmHttpsA76xx
     /**
      * @brief  POSTFile
      * @note   Send file to server
-     * @param  *filepath:File path and file name, full path required
+     * @param  *filepath:File path and file name, full path required. C:/file for local storage and D:/file for SD card
      * @param  method:  0 = GET 1 = POST 2 = HEAD 3 = DELETE
      * @param  sendFileAsBody: 0 = Send file as HTTP header and body , 1 = Send file as Body
      * @retval httpCode, -1 = failed
      */
     int https_post_file(const char *filepath, uint8_t method = 1, bool sendFileAsBody = 1)
     {
+        // A76XX Series_AT Command Manual_V1.09, Page 363
         // AT+HTTPPOSTFILE=<filename>[,<path>[,<method>[,<send_header>]]]
-        uint8_t path = 1;
-        if (!filepath)return -1;
-        if (&filepath[3] == NULL)return -1;
-        if (filepath[0] == 'd' || filepath[0] == 'D') {
-            path = 2;
-        }
-        thisModem().sendAT("+HTTPPOSTFILE=\"", &filepath[3], "\",", path, ',', method, ',', sendFileAsBody);
+        // filename: full path required. C:/file for local storage and D:/file for SD card
+        if (!filepath || strlen(filepath) < 4) return -1; // no file
+        uint8_t path = filepath[0] == 'd' || filepath[0] == 'D' ? 2 : 1; // storage (2 for SD or 1 for local)
+        thisModem().sendAT("+HTTPPOSTFILE=\"", filepath[3], "\",", path, ',', method, ',', sendFileAsBody);
         if (thisModem().waitResponse(120000UL) != 1) {
             return -1;
         }