diff --git a/Documentation/config/advice.txt b/Documentation/config/advice.txt
index a00d0100a8..0d1e04f1ed 100644
--- a/Documentation/config/advice.txt
+++ b/Documentation/config/advice.txt
@@ -136,4 +136,7 @@ advice.*::
 		Advice shown when either linkgit:git-add[1] or linkgit:git-rm[1]
 		is asked to update index entries outside the current sparse
 		checkout.
+	useCoreFSMonitorConfig::
+		Advice shown if the deprecated 'core.useBuiltinFSMonitor' config
+		setting is in use.
 --
diff --git a/advice.c b/advice.c
index 6fda9edbc2..89cf9347ca 100644
--- a/advice.c
+++ b/advice.c
@@ -74,6 +74,7 @@ static struct {
 	[ADVICE_SUBMODULE_ALTERNATE_ERROR_STRATEGY_DIE] = { "submoduleAlternateErrorStrategyDie", 1 },
 	[ADVICE_SUBMODULES_NOT_UPDATED] 		= { "submodulesNotUpdated", 1 },
 	[ADVICE_UPDATE_SPARSE_PATH]			= { "updateSparsePath", 1 },
+	[ADVICE_USE_CORE_FSMONITOR_CONFIG]		= { "useCoreFSMonitorConfig", 1 },
 	[ADVICE_WAITING_FOR_EDITOR]			= { "waitingForEditor", 1 },
 };
 
diff --git a/advice.h b/advice.h
index 7ddc6cbc1a..7d14e382d7 100644
--- a/advice.h
+++ b/advice.h
@@ -48,6 +48,7 @@ struct string_list;
 	ADVICE_SUBMODULE_ALTERNATE_ERROR_STRATEGY_DIE,
 	ADVICE_SUBMODULES_NOT_UPDATED,
 	ADVICE_UPDATE_SPARSE_PATH,
+	ADVICE_USE_CORE_FSMONITOR_CONFIG,
 	ADVICE_WAITING_FOR_EDITOR,
 	ADVICE_SKIPPED_CHERRY_PICKS,
 };
diff --git a/fsmonitor-settings.c b/fsmonitor-settings.c
index 60d5eaee49..dee197a29b 100644
--- a/fsmonitor-settings.c
+++ b/fsmonitor-settings.c
@@ -48,6 +48,29 @@ static int check_for_incompatible(struct repository *r)
 	return 0;
 }
 
+static int check_deprecated_builtin_config(struct repository *r)
+{
+	int core_use_builtin_fsmonitor;
+
+	/*
+	 * If 'core.useBuiltinFSMonitor' is set, print a deprecation warning
+	 * suggesting the use of 'core.fsmonitor' instead. If the config is
+	 * set to true, set the appropriate mode and return 1 indicating that
+	 * the check resulted the config being set by this (deprecated) setting.
+	 */
+	if(!repo_config_get_bool(r, "core.useBuiltinFSMonitor", &core_use_builtin_fsmonitor)) {
+		advise_if_enabled(ADVICE_USE_CORE_FSMONITOR_CONFIG,
+				  _("core.useBuiltinFSMonitor will be deprecated "
+				    "soon; use core.fsmonitor instead"));
+		if (core_use_builtin_fsmonitor) {
+			fsm_settings__set_ipc(r);
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
 static void lookup_fsmonitor_settings(struct repository *r)
 {
 	struct fsmonitor_settings *s;
@@ -78,12 +101,16 @@ static void lookup_fsmonitor_settings(struct repository *r)
 		return;
 
 	case 1: /* config value was unset */
+		if (check_deprecated_builtin_config(r))
+			return;
+
 		const_str = getenv("GIT_TEST_FSMONITOR");
 		break;
 
 	case -1: /* config value set to an arbitrary string */
-		if (repo_config_get_pathname(r, "core.fsmonitor", &const_str))
-			return; /* should not happen */
+		if (check_deprecated_builtin_config(r) ||
+		    repo_config_get_pathname(r, "core.fsmonitor", &const_str))
+			return;
 		break;
 
 	default: /* should not happen */
diff --git a/repo-settings.c b/repo-settings.c
index 2dfcb2b654..459041f65c 100644
--- a/repo-settings.c
+++ b/repo-settings.c
@@ -2,7 +2,8 @@
 #include "config.h"
 #include "repository.h"
 #include "midx.h"
-#include "compat/fsmonitor/fsm-listen.h"
+#include "fsmonitor-ipc.h"
+#include "fsmonitor-settings.h"
 
 static void repo_cfg_bool(struct repository *r, const char *key, int *dest,
 			  int def)
@@ -36,6 +37,30 @@ void prepare_repo_settings(struct repository *r)
 	/* Defaults modified by feature.* */
 	if (experimental) {
 		r->settings.fetch_negotiation_algorithm = FETCH_NEGOTIATION_SKIPPING;
+
+		/*
+		 * Force enable the builtin FSMonitor (unless the repo
+		 * is incompatible or they've already selected it or
+		 * the hook version).  But only if they haven't
+		 * explicitly turned it off -- so only if our config
+		 * value is UNSET.
+		 *
+		 * lookup_fsmonitor_settings() and check_for_ipc() do
+		 * not distinguish between explicitly set FALSE and
+		 * UNSET, so we re-test for an UNSET config key here.
+		 *
+		 * I'm not sure I want to fix fsmonitor-settings.c to
+		 * have more than one _DISABLED state since our usage
+		 * here is only to support this experimental period
+		 * (and I don't want to overload the _reason field
+		 * because it describes incompabilities).
+		 */
+		if (manyfiles &&
+		    fsmonitor_ipc__is_supported()  &&
+		    fsm_settings__get_mode(r) == FSMONITOR_MODE_DISABLED &&
+		    repo_config_get_maybe_bool(r, "core.fsmonitor", &value) > 0 &&
+		    repo_config_get_bool(r, "core.useBuiltinFSMonitor", &value))
+			fsm_settings__set_ipc(r);
 	}
 	if (manyfiles) {
 		r->settings.index_version = 4;