diff --git a/H/YapText.h b/H/YapText.h
index 7d5ac5a83..2c5738203 100644
--- a/H/YapText.h
+++ b/H/YapText.h
@@ -190,7 +190,7 @@ INLINE_ONLY inline EXTERN utf8proc_ssize_t get_utf8(const utf8proc_uint8_t *ptr,
   if (rc < 0) {
     LOCAL_ActiveError->errorNo = REPRESENTATION_ERROR_IN_CHARACTER_CODE;
   }
-  return rc;
+  return rc < 1 ? 1 : rc;
 }
 
 INLINE_ONLY inline EXTERN utf8proc_ssize_t put_utf8(utf8proc_uint8_t *ptr,
@@ -202,7 +202,7 @@ INLINE_ONLY inline EXTERN utf8proc_ssize_t put_utf8(utf8proc_uint8_t *ptr,
   if (rc < 0) {
     LOCAL_ActiveError->errorNo = REPRESENTATION_ERROR_CHARACTER_CODE;
   }
-  return rc;
+  return rc < 1 ? 1 : rc;
 }
 
 inline static const utf8proc_uint8_t *skip_utf8(const utf8proc_uint8_t *pt,
diff --git a/os/format.c b/os/format.c
index 1b3faff12..00f40802c 100644
--- a/os/format.c
+++ b/os/format.c
@@ -277,8 +277,10 @@ static int format_print_str(Int sno, Int size, Int has_size, Term args,
     const unsigned char *pt = UStringOfTerm(args);
     while (*pt && (!has_size || size > 0)) {
       utf8proc_int32_t ch;
-      pt += get_utf8(pt, -1, &ch);
-      f_putc(sno, ch);
+      
+      if ((pt += get_utf8(pt, -1, &ch)) > 0) {
+	f_putc(sno, ch);
+      }	
     }
   } else {
     while (!has_size || size > 0) {