diff --git a/mercurial/merge.py b/mercurial/merge.py
--- a/mercurial/merge.py
+++ b/mercurial/merge.py
@@ -1368,10 +1368,6 @@
     usemergedriver = not overwrite and mergeactions and ms.mergedriver
 
     if usemergedriver:
-        if wctx.isinmemory():
-            raise error.InMemoryMergeConflictsError(
-                b"in-memory merge does not support mergedriver"
-            )
         ms.commit()
         proceed = driverpreprocess(repo, ms, wctx, labels=labels)
         # the driver might leave some files unresolved