diff --git a/include/mbedtls/debug.h b/include/mbedtls/debug.h
index ecab1023f9..e11f373831 100644
--- a/include/mbedtls/debug.h
+++ b/include/mbedtls/debug.h
@@ -89,10 +89,12 @@
 #if defined(__MINGW32__) || (defined(_MSC_VER) && _MSC_VER < 1900)
    #include <inttypes.h>
    #define MBEDTLS_PRINTF_SIZET     PRIuPTR
+   #define MBEDTLS_PRINTF_SIZET_HEX PRIxPTR
    #define MBEDTLS_PRINTF_LONGLONG  "I64d"
 #else \
     /* defined(__MINGW32__) || (defined(_MSC_VER) && _MSC_VER < 1900) */
    #define MBEDTLS_PRINTF_SIZET     "zu"
+   #define MBEDTLS_PRINTF_SIZET_HEX "zx"
    #define MBEDTLS_PRINTF_LONGLONG  "lld"
 #endif \
     /* defined(__MINGW32__) || (defined(_MSC_VER) && _MSC_VER < 1900) */
diff --git a/library/debug.c b/library/debug.c
index 8ac4b0ba54..0721d60a14 100644
--- a/library/debug.c
+++ b/library/debug.c
@@ -154,12 +154,13 @@ static void mbedtls_debug_print_buf_ext(const mbedtls_ssl_context *ssl, int leve
         return;
     }
 
-    mbedtls_snprintf(str, sizeof(str), "dumping '%s' (%zu bytes)\n", text, len);
+    mbedtls_snprintf(str, sizeof(str), "dumping '%s' (%" MBEDTLS_PRINTF_SIZET " bytes)\n",
+                     text, len);
     debug_send_line(ssl, level, file, line, str);
 
     while (len > 0) {
         memset(str, 0, sizeof(str));
-        idx = mbedtls_snprintf(str, sizeof(str), "%04zx: ", curr_offset);
+        idx = mbedtls_snprintf(str, sizeof(str), "%04" MBEDTLS_PRINTF_SIZET_HEX ": ", curr_offset);
         chunk_len = (len >= 16) ? 16 : len;
         mbedtls_debug_print_buf_one_line(str + idx, sizeof(str) - idx,
                                          &buf[curr_offset], chunk_len,