diff --git a/src/builtins/history.cpp b/src/builtins/history.cpp
index e6b6bbe43..2f43cc5c4 100644
--- a/src/builtins/history.cpp
+++ b/src/builtins/history.cpp
@@ -305,6 +305,12 @@ maybe_t<int> builtin_history(parser_t &parser, io_streams_t &streams, const wcha
                 break;
             }
 
+            if (in_private_mode(parser.vars())) {
+                streams.err.append_format(
+                                          _(L"%ls: can't merge history in private mode\n"), cmd);
+                status = STATUS_INVALID_ARGS;
+                break;
+            }
             history->incorporate_external_changes();
             break;
         }
diff --git a/tests/checks/history.fish b/tests/checks/history.fish
index 7afe35b60..53a62d463 100644
--- a/tests/checks/history.fish
+++ b/tests/checks/history.fish
@@ -66,3 +66,7 @@ builtin history -t merge
 # Now do a history command that should succeed so we exit with a zero,
 # success, status.
 builtin history save
+
+set -g fish_private_mode 1
+builtin history merge
+#CHECKERR: history: can't merge history in private mode