diff --git a/third_party/copybara/copy.bara.sky b/third_party/copybara/copy.bara.sky
index 78aaeb18cd..ea9234c72c 100644
--- a/third_party/copybara/copy.bara.sky
+++ b/third_party/copybara/copy.bara.sky
@@ -18,7 +18,10 @@ core.workflow(
     ),
     authoring = authoring.pass_thru("Default email <noreply+copybara@lukegb.com>"),
     transformations = [
-        patch.apply(patches = ["patches/0001-Make-Mercurial-at-least-slightly-usable.patch"]),
+        patch.apply(patches = [
+            "patches/0001-Make-Mercurial-at-least-slightly-usable.patch",
+            "patches/0002-HgRepository-HGPLAIN.patch",
+        ]),
         core.move("", "third_party/copybara"),
     ],
 )
diff --git a/third_party/copybara/java/com/google/copybara/hg/HgRepository.java b/third_party/copybara/java/com/google/copybara/hg/HgRepository.java
index 40bc2663c4..40c96bd012 100644
--- a/third_party/copybara/java/com/google/copybara/hg/HgRepository.java
+++ b/third_party/copybara/java/com/google/copybara/hg/HgRepository.java
@@ -51,6 +51,8 @@ import java.time.ZonedDateTime;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.HashMap;
+import java.util.Map;
 import javax.annotation.Nullable;
 
 /**
@@ -240,8 +242,10 @@ public class HgRepository {
     List<String> allParams = new ArrayList<>(Iterables.size(params) + 1);
     allParams.add("hg"); //TODO(jlliu): resolve Hg binary here
     Iterables.addAll(allParams, params);
+    Map<String, String> environment = new HashMap<>();
+    environment.put("HGPLAIN", "");
     Command cmd = new Command(
-        Iterables.toArray(allParams, String.class), null, cwd.toFile());
+        Iterables.toArray(allParams, String.class), environment, cwd.toFile());
         //TODO(jlliu): have environment vars
     CommandRunner runner = new CommandRunner(cmd, timeout).withVerbose(verbose);
     return
diff --git a/third_party/copybara/patches/0002-HgRepository-HGPLAIN.patch b/third_party/copybara/patches/0002-HgRepository-HGPLAIN.patch
new file mode 100644
index 0000000000..43bdb5c4da
--- /dev/null
+++ b/third_party/copybara/patches/0002-HgRepository-HGPLAIN.patch
@@ -0,0 +1,32 @@
+# HG changeset patch
+# User Luke Granger-Brown <hg@lukegb.com>
+# Date 1589670391 -3600
+#      Sun May 17 00:06:31 2020 +0100
+# Node ID ac30ad2187112d227da97d68c1996663fabfa1f6
+# Parent  478b958c38cb0d2e354076b55b21232f69af5fcc
+third_party/copybara: patch HgRepository to use HGPLAIN
+
+diff --git a/java/com/google/copybara/hg/HgRepository.java b/java/com/google/copybara/hg/HgRepository.java
+--- a/java/com/google/copybara/hg/HgRepository.java
++++ b/java/com/google/copybara/hg/HgRepository.java
+@@ -51,6 +51,8 @@ import java.time.ZonedDateTime;
+ import java.util.ArrayList;
+ import java.util.Arrays;
+ import java.util.List;
++import java.util.HashMap;
++import java.util.Map;
+ import javax.annotation.Nullable;
+ 
+ /**
+@@ -240,8 +242,10 @@ public class HgRepository {
+     List<String> allParams = new ArrayList<>(Iterables.size(params) + 1);
+     allParams.add("hg"); //TODO(jlliu): resolve Hg binary here
+     Iterables.addAll(allParams, params);
++    Map<String, String> environment = new HashMap<>();
++    environment.put("HGPLAIN", "");
+     Command cmd = new Command(
+-        Iterables.toArray(allParams, String.class), null, cwd.toFile());
++        Iterables.toArray(allParams, String.class), environment, cwd.toFile());
+         //TODO(jlliu): have environment vars
+     CommandRunner runner = new CommandRunner(cmd, timeout).withVerbose(verbose);
+     return