diff --git a/libavformat/avio.h b/libavformat/avio.h
index abe13b2719..c3c0b73f2c 100644
--- a/libavformat/avio.h
+++ b/libavformat/avio.h
@@ -458,7 +458,7 @@ attribute_deprecated
 int url_feof(AVIOContext *s);
 #endif
 
-/** @warning currently size is limited */
+/** @warning Writes up to 4 KiB per call */
 int avio_printf(AVIOContext *s, const char *fmt, ...) av_printf_format(2, 3);
 
 /**
diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
index c2aa8dc96e..57cbf8311d 100644
--- a/libavformat/aviobuf.c
+++ b/libavformat/aviobuf.c
@@ -968,7 +968,7 @@ int avio_closep(AVIOContext **s)
 int avio_printf(AVIOContext *s, const char *fmt, ...)
 {
     va_list ap;
-    char buf[4096];
+    char buf[4096]; /* update doc entry in avio.h if changed */
     int ret;
 
     va_start(ap, fmt);