Index: subversion/svn/conflict-callbacks.c
===================================================================
--- subversion/svn/conflict-callbacks.c	(revision 1764640)
+++ subversion/svn/conflict-callbacks.c	(working copy)
@@ -1812,6 +1812,7 @@
   const char *my_abspath = NULL;
   const char *their_abspath = NULL;
   const char *merged_abspath = svn_client_conflict_get_local_abspath(conflict);
+  const char *mime_type;
   svn_boolean_t text_conflicted;
   apr_array_header_t *props_conflicted;
   svn_boolean_t tree_conflicted;
@@ -1845,7 +1846,13 @@
       *option_id = svn_client_conflict_option_base_text;
       break;
     case svn_cl__accept_working:
-      *option_id = svn_client_conflict_option_merged_text;
+      {
+        mime_type = svn_client_conflict_text_get_mime_type(conflict);
+        if (mime_type && svn_mime_type_is_binary(mime_type))
+          *option_id = svn_client_conflict_option_working_text;
+        else
+          *option_id = svn_client_conflict_option_merged_text;
+      }
       break;
     case svn_cl__accept_mine_conflict:
       *option_id = svn_client_conflict_option_working_text_where_conflicted;