diff --git a/keyboards/crkbd/rev1/keymaps/maat/config.h b/keyboards/crkbd/rev1/keymaps/maat/config.h
index 10b23222d6d..b062d64ab1a 100644
--- a/keyboards/crkbd/rev1/keymaps/maat/config.h
+++ b/keyboards/crkbd/rev1/keymaps/maat/config.h
@@ -29,3 +29,6 @@
 #define RAW_USAGE_PAGE 0xFF60
 #define RAW_USAGE 0x61
 // -- App Companion end
+
+// Apply custom shift keys only on layer 4 (numbers).
+#define CUSTOM_SHIFT_KEYS_LAYER_MASK (1 << 4)
diff --git a/keyboards/crkbd/rev1/keymaps/maat/keymap.c b/keyboards/crkbd/rev1/keymaps/maat/keymap.c
index 7f3f5b73352..c8c4de9ae2c 100644
--- a/keyboards/crkbd/rev1/keymaps/maat/keymap.c
+++ b/keyboards/crkbd/rev1/keymaps/maat/keymap.c
@@ -1,8 +1,19 @@
 // clang-format off
+#include "keycodes.h"
 #include QMK_KEYBOARD_H
 #include "raw_hid.h"
 #include "keymap.h"
 
+// https://github.com/getreuer/qmk-modules/tree/main/custom_shift_keys
+const custom_shift_key_t custom_shift_keys[] = {
+  {KC_2, KC_COMMA},
+  {KC_3, KC_DOT},
+  {KC_5, KC_LABK},
+  {KC_6, KC_RABK},
+  {KC_7, KC_LPRN},
+  {KC_9, KC_RPRN},
+};
+
 // Notifies the host of the layer change using raw HID
 // https://docs.qmk.fm/features/rawhid#usage
 //
diff --git a/keyboards/crkbd/rev1/keymaps/maat/keymap.json b/keyboards/crkbd/rev1/keymaps/maat/keymap.json
index 9111cf15497..5697adfe78c 100644
--- a/keyboards/crkbd/rev1/keymaps/maat/keymap.json
+++ b/keyboards/crkbd/rev1/keymaps/maat/keymap.json
@@ -1,3 +1,3 @@
 {
-    "modules": ["jgandert/predictive_tap_hold"]
+    "modules": ["getreuer/custom_shift_keys", "jgandert/predictive_tap_hold"]
 }