diff --git a/src/update-mime-database.cpp b/src/update-mime-database.cpp
index f3650b1..b2524a7 100644
--- a/src/update-mime-database.cpp
+++ b/src/update-mime-database.cpp
@@ -1317,7 +1317,7 @@ static char *parse_string_mask(const char *mask, int len, GError **error)
 		if (i >= len * 2)
 		{
 			g_set_error(error, MIME_ERROR, 0,
-				"Mask is longer than value");
+				"Mask length %i is longer than value length %i",i,len*2);
 			goto err;
 		}