diff --git a/os/various/chprintf.c b/os/various/chprintf.c
index 0feee72c3..78453f52b 100644
--- a/os/various/chprintf.c
+++ b/os/various/chprintf.c
@@ -246,12 +246,12 @@ unsigned_common:
         chSequentialStreamPut(chp, (uint8_t)*s++);
         i--;
       }
-      do
+      do {
         chSequentialStreamPut(chp, (uint8_t)filler);
-      while (++width != 0);
+      } while (++width != 0);
     }
-    chSequentialStreamWrite(chp, (uint8_t*)s, i);
-    s += i;
+    while (--i >= 0)
+      chSequentialStreamPut(chp, (uint8_t)*s++);
 
     while (width) {
       chSequentialStreamPut(chp, (uint8_t)filler);