diff --git a/libavdevice/decklink_common.cpp b/libavdevice/decklink_common.cpp
index b88d6c6219..130e70b2ca 100644
--- a/libavdevice/decklink_common.cpp
+++ b/libavdevice/decklink_common.cpp
@@ -77,7 +77,7 @@ static IDeckLinkIterator *decklink_create_iterator(AVFormatContext *avctx)
     return iter;
 }
 
-int decklink_get_attr_string(IDeckLink *dl, BMDDeckLinkAttributeID cfg_id, const char **s)
+static int decklink_get_attr_string(IDeckLink *dl, BMDDeckLinkAttributeID cfg_id, const char **s)
 {
     DECKLINK_STR tmp;
     HRESULT hr;