diff --git a/hgext/fix.py b/hgext/fix.py
--- a/hgext/fix.py
+++ b/hgext/fix.py
@@ -283,20 +283,29 @@
         # There are no data dependencies between the workers fixing each file
         # revision, so we can use all available parallelism.
         def getfixes(items):
-            for rev, path in items:
-                ctx = repo[rev]
+            for srcrev, path, dstrevs in items:
+                ctx = repo[srcrev]
                 olddata = ctx[path].data()
                 metadata, newdata = fixfile(
-                    ui, repo, opts, fixers, ctx, path, basepaths, basectxs[rev]
+                    ui,
+                    repo,
+                    opts,
+                    fixers,
+                    ctx,
+                    path,
+                    basepaths,
+                    basectxs[srcrev],
                 )
-                # Don't waste memory/time passing unchanged content back, but
-                # produce one result per item either way.
-                yield (
-                    rev,
-                    path,
-                    metadata,
-                    newdata if newdata != olddata else None,
-                )
+                # We ungroup the work items now, because the code that consumes
+                # these results has to handle each dstrev separately, and in
+                # topological order. Because these are handled in topological
+                # order, it's important that we pass around references to
+                # "newdata" instead of copying it. Otherwise, we would be
+                # keeping more copies of file content in memory at a time than
+                # if we hadn't bothered to group/deduplicate the work items.
+                data = newdata if newdata != olddata else None
+                for dstrev in dstrevs:
+                    yield (dstrev, path, metadata, data)
 
         results = worker.worker(
             ui, 1.0, getfixes, tuple(), workqueue, threadsafe=False
@@ -392,7 +401,7 @@
     items by ascending revision number to match the order in which we commit
     the fixes later.
     """
-    workqueue = []
+    dstrevmap = collections.defaultdict(list)
     numitems = collections.defaultdict(int)
     maxfilesize = ui.configbytes(b'fix', b'maxfilesize')
     for rev in sorted(revstofix):
@@ -410,8 +419,13 @@
                     % (util.bytecount(maxfilesize), path)
                 )
                 continue
-            workqueue.append((rev, path))
+            baserevs = tuple(ctx.rev() for ctx in basectxs[rev])
+            dstrevmap[(fctx.filerev(), baserevs, path)].append(rev)
             numitems[rev] += 1
+    workqueue = [
+        (dstrevs[0], path, dstrevs)
+        for (filerev, baserevs, path), dstrevs in dstrevmap.items()
+    ]
     return workqueue, numitems
 
 
@@ -516,9 +530,9 @@
         return {}
 
     basepaths = {}
-    for rev, path in workqueue:
-        fixctx = repo[rev]
-        for basectx in basectxs[rev]:
+    for srcrev, path, dstrevs in workqueue:
+        fixctx = repo[srcrev]
+        for basectx in basectxs[srcrev]:
             basepath = copies.pathcopies(basectx, fixctx).get(path, path)
             if basepath in basectx:
                 basepaths[(basectx.rev(), fixctx.rev(), path)] = basepath
@@ -641,10 +655,10 @@
     toprefetch = set()
 
     # Prefetch the files that will be fixed.
-    for rev, path in workqueue:
-        if rev == wdirrev:
+    for srcrev, path, dstrevs in workqueue:
+        if srcrev == wdirrev:
             continue
-        toprefetch.add((rev, path))
+        toprefetch.add((srcrev, path))
 
     # Prefetch the base contents for lineranges().
     for (baserev, fixrev, path), basepath in basepaths.items():
diff --git a/tests/test-fix.t b/tests/test-fix.t
--- a/tests/test-fix.t
+++ b/tests/test-fix.t
@@ -1758,8 +1758,8 @@
   $ cat $LOGFILE | sort | uniq -c
         4 bar.log
         4 baz.log
-        4 foo.log
-        4 qux.log
+        3 foo.log
+        2 qux.log
 
   $ cd ..