diff --git a/mercurial/debugcommands.py b/mercurial/debugcommands.py
--- a/mercurial/debugcommands.py
+++ b/mercurial/debugcommands.py
@@ -2016,6 +2016,7 @@
             b'")}'
             b'{extras % "  extra: {key} = {value}\n"}'
             b'"}'
+            b'{extras % "extra: {file} ({key} = {value})\n"}'
         )
 
     ms = mergestatemod.mergestate.read(repo)
@@ -2069,6 +2070,18 @@
 
     fm_files.end()
 
+    fm_extras = fm.nested(b'extras')
+    for f, d in sorted(pycompat.iteritems(ms._stateextras)):
+        if f in ms:
+            # If file is in mergestate, we have already processed it's extras
+            continue
+        for k, v in pycompat.iteritems(d):
+            fm_extras.startitem()
+            fm_extras.data(file=f)
+            fm_extras.data(key=k)
+            fm_extras.data(value=v)
+    fm_extras.end()
+
     fm.end()
 
 
diff --git a/tests/test-resolve.t b/tests/test-resolve.t
--- a/tests/test-resolve.t
+++ b/tests/test-resolve.t
@@ -328,6 +328,7 @@
   [
    {
     "commits": [{"label": "working copy", "name": "local", "node": "57653b9f834a4493f7240b0681efcb9ae7cab745"}, {"label": "merge rev", "name": "other", "node": "dc77451844e37f03f5c559e3b8529b2b48d381d1"}],
+    "extras": [],
     "files": [{"ancestor_node": "2ed2a3912a0b24502043eae84ee4b279c18b90dd", "ancestor_path": "file1", "extras": [{"key": "ancestorlinknode", "value": "99726c03216e233810a2564cbc0adfe395007eac"}], "local_flags": "", "local_key": "60b27f004e454aca81b0480209cce5081ec52390", "local_path": "file1", "other_node": "6f4310b00b9a147241b071a60c28a650827fb03d", "other_path": "file1", "path": "file1", "state": "r"}, {"ancestor_node": "2ed2a3912a0b24502043eae84ee4b279c18b90dd", "ancestor_path": "file2", "extras": [{"key": "ancestorlinknode", "value": "99726c03216e233810a2564cbc0adfe395007eac"}], "local_flags": "", "local_key": "cb99b709a1978bd205ab9dfd4c5aaa1fc91c7523", "local_path": "file2", "other_node": "6f4310b00b9a147241b071a60c28a650827fb03d", "other_path": "file2", "path": "file2", "state": "u"}]
    }
   ]