diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 8378c13..c150d3d 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1504,7 +1504,7 @@
  * @...: Arguments for the format string
  *
  * The return value is the number of characters written into @buf not including
- * the trailing '\0'. If @size is <= 0 the function returns 0.
+ * the trailing '\0'. If @size is == 0 the function returns 0.
  */
 
 int scnprintf(char *buf, size_t size, const char *fmt, ...)
@@ -1516,7 +1516,11 @@
 	i = vsnprintf(buf, size, fmt, args);
 	va_end(args);
 
-	return (i >= size) ? (size - 1) : i;
+	if (likely(i < size))
+		return i;
+	if (size != 0)
+		return size - 1;
+	return 0;
 }
 EXPORT_SYMBOL(scnprintf);