diff --git a/ChangeLog.d/fix-mingw-ansi-stdio.txt b/ChangeLog.d/fix-mingw-ansi-stdio.txt
new file mode 100644
index 0000000000..d9293d95ca
--- /dev/null
+++ b/ChangeLog.d/fix-mingw-ansi-stdio.txt
@@ -0,0 +1,4 @@
+Bugfix
+   * Fix a build failure with MinGW when the __USE_MINGW_ANSI_STDIO option
+     is set. This was caused by the wrong format specifier being used to
+     print long long values (MBEDTLS_PRINTF_LONGLONG).
diff --git a/include/mbedtls/debug.h b/include/mbedtls/debug.h
index e6f5dadb14..45bf390a04 100644
--- a/include/mbedtls/debug.h
+++ b/include/mbedtls/debug.h
@@ -111,7 +111,7 @@
 #if defined(__MINGW32__) || (defined(_MSC_VER) && _MSC_VER < 1900)
    #include <inttypes.h>
    #define MBEDTLS_PRINTF_SIZET     PRIuPTR
-   #define MBEDTLS_PRINTF_LONGLONG  "I64d"
+   #define MBEDTLS_PRINTF_LONGLONG  PRId64
 #else \
     /* defined(__MINGW32__) || (defined(_MSC_VER) && _MSC_VER < 1900) */
    #define MBEDTLS_PRINTF_SIZET     "zu"