diff --git a/os/various/chprintf.c b/os/various/chprintf.c
index 0b9ff2da5..688df137a 100644
--- a/os/various/chprintf.c
+++ b/os/various/chprintf.c
@@ -196,6 +196,8 @@ void chprintf(BaseSequentialStream *chp, const char *fmt, ...) {
       break;
     case 'D':
     case 'd':
+    case 'I':
+    case 'i':
       if (is_long)
         l = va_arg(ap, long);
       else
diff --git a/readme.txt b/readme.txt
index 07762bf05..6c54adbb4 100644
--- a/readme.txt
+++ b/readme.txt
@@ -89,6 +89,7 @@
 *****************************************************************************
 
 *** 2.5.2 ***
+- FIX: Fixed add %i to chprintf (bug #401).
 - FIX: Fixed STM32F051 various (bug #400).
 - FIX: Fixed STM32F103 HSI configuration (bug #399).
 - FIX: Fixed patch to allow simulator to be restarted quicker (bug #398).