diff --git a/libavformat/mxf.h b/libavformat/mxf.h
index a2d919aa0c..24432071ee 100644
--- a/libavformat/mxf.h
+++ b/libavformat/mxf.h
@@ -79,6 +79,18 @@ extern const MXFCodecUL ff_mxf_pixel_format_uls[];
 int ff_mxf_decode_pixel_layout(const char pixel_layout[16], enum AVPixelFormat *pix_fmt);
 const MXFSamplesPerFrame *ff_mxf_get_samples_per_frame(AVFormatContext *s, AVRational time_base);
 
+#define PRIxUID                             \
+    "%02x.%02x.%02x.%02x."                  \
+    "%02x.%02x.%02x.%02x."                  \
+    "%02x.%02x.%02x.%02x."                  \
+    "%02x.%02x.%02x.%02x"
+
+#define UID_ARG(x) \
+    (x)[0],  (x)[1],  (x)[2],  (x)[3],      \
+    (x)[4],  (x)[5],  (x)[6],  (x)[7],      \
+    (x)[8],  (x)[9],  (x)[10], (x)[11],     \
+    (x)[12], (x)[13], (x)[14], (x)[15]      \
+
 #ifdef DEBUG
 #define PRINT_KEY(pc, s, x)                         \
     av_log(pc, AV_LOG_VERBOSE,                      \
diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
index ba76577e13..410c13b30d 100644
--- a/libavformat/mxfdec.c
+++ b/libavformat/mxfdec.c
@@ -2185,6 +2185,9 @@ static int mxf_read_header(AVFormatContext *s)
                     return res;
                 }
                 break;
+            } else {
+                av_log(s, AV_LOG_VERBOSE, "Dark key " PRIxUID "\n",
+                       UID_ARG(klv.key));
             }
         }
         if (!metadata->read)