diff --git a/Documentation/git-merge-tree.txt b/Documentation/git-merge-tree.txt
index 0b6a8a19b1f98f..cf0578f9b5e86d 100644
--- a/Documentation/git-merge-tree.txt
+++ b/Documentation/git-merge-tree.txt
@@ -40,11 +40,17 @@ After the merge completes, a new toplevel tree object is created.  See
 OPTIONS
 -------
 
+--stdin::
+	Read the commits to merge from the standard input rather than
+	the command-line. See <<INPUT,INPUT FORMAT>> below for more
+	information.  Implies `-z`.
+
 -z::
 	Do not quote filenames in the <Conflicted file info> section,
 	and end each filename with a NUL character rather than
 	newline.  Also begin the messages section with a NUL character
-	instead of a newline.  See <<OUTPUT>> below for more information.
+	instead of a newline.  See <<OUTPUT,OUTPUT>> below for more
+	information.
 
 --name-only::
 	In the Conflicted file info section, instead of writing a list
@@ -116,8 +122,6 @@ This is an integer status followed by a NUL character.  The integer status is:
 
      0: merge had conflicts
      1: merge was clean
-     <0: something prevented the merge from running (e.g. access to repository
-	 objects denied by filesystem)
 
 [[OIDTLT]]
 OID of toplevel tree
@@ -235,6 +239,7 @@ with linkgit:git-merge[1]:
   * any messages that would have been printed to stdout (the
     <<IM,Informational messages>>)
 
+[[INPUT]]
 INPUT FORMAT
 ------------
 'git merge-tree --stdin' input format is fully text based. Each line
diff --git a/builtin/merge-tree.c b/builtin/merge-tree.c
index 9a6c8b4e4cf212..3ec7127b3a6b3f 100644
--- a/builtin/merge-tree.c
+++ b/builtin/merge-tree.c
@@ -18,6 +18,7 @@
 #include "tree.h"
 #include "config.h"
 #include "strvec.h"
+#include "write-or-die.h"
 
 static int line_termination = '\n';
 
@@ -575,7 +576,7 @@ int cmd_merge_tree(int argc,
 	};
 
 	/* Init merge options */
-	init_ui_merge_options(&o.merge_options, the_repository);
+	init_basic_merge_options(&o.merge_options, the_repository);
 
 	/* Parse arguments */
 	original_argc = argc - 1; /* ignoring argv[0] */
@@ -600,7 +601,6 @@ int cmd_merge_tree(int argc,
 		line_termination = '\0';
 		while (strbuf_getline_lf(&buf, stdin) != EOF) {
 			struct strbuf **split;
-			int result;
 			const char *input_merge_base = NULL;
 
 			split = strbuf_split(&buf, ' ');
@@ -617,15 +617,14 @@ int cmd_merge_tree(int argc,
 			if (input_merge_base && split[2] && split[3] && !split[4]) {
 				strbuf_rtrim(split[2]);
 				strbuf_rtrim(split[3]);
-				result = real_merge(&o, input_merge_base, split[2]->buf, split[3]->buf, prefix);
+				real_merge(&o, input_merge_base, split[2]->buf, split[3]->buf, prefix);
 			} else if (!input_merge_base && !split[2]) {
-				result = real_merge(&o, NULL, split[0]->buf, split[1]->buf, prefix);
+				real_merge(&o, NULL, split[0]->buf, split[1]->buf, prefix);
 			} else {
 				die(_("malformed input line: '%s'."), buf.buf);
 			}
+			maybe_flush_or_die(stdout, "stdout");
 
-			if (result < 0)
-				die(_("merging cannot continue; got unclean result of %d"), result);
 			strbuf_list_free(split);
 		}
 		strbuf_release(&buf);