diff --git a/Changes.md b/Changes.md
index 2cea334..c40d521 100644
--- a/Changes.md
+++ b/Changes.md
@@ -1,5 +1,23 @@
 # Build System Changes for Android.mk Writers
 
+## PRODUCT_STATIC_BOOT_CONTROL_HAL is obsolete {#PRODUCT_STATIC_BOOT_CONTROL_HAL}
+
+`PRODUCT_STATIC_BOOT_CONTROL_HAL` was the workaround to allow sideloading with
+statically linked boot control HAL, before shared library HALs were supported
+under recovery. Android Q has added such support (HALs will be loaded in
+passthrough mode), and the workarounds are being removed. Targets should build
+and install the recovery variant of boot control HAL modules into recovery
+image, similar to the ones installed for normal boot. See the change to
+crosshatch for example of this:
+
+* [device/google/crosshatch/bootctrl/Android.bp] for `bootctrl.sdm845` building
+  rules
+* [device/google/crosshatch/device.mk] for installing `bootctrl.sdm845.recovery`
+  and `android.hardware.boot@1.0-impl.recovery` into recovery image
+
+[device/google/crosshatch/bootctrl/Android.bp]: https://android.googlesource.com/device/google/crosshatch/+/master/bootctrl/Android.bp
+[device/google/crosshatch/device.mk]: https://android.googlesource.com/device/google/crosshatch/+/master/device.mk
+
 ## Deprecation of `BUILD_*` module types
 
 See [build/make/Deprecation.md](Deprecation.md) for the current status.
diff --git a/core/config.mk b/core/config.mk
index 6830475..4a26a76 100644
--- a/core/config.mk
+++ b/core/config.mk
@@ -100,6 +100,7 @@
 $(KATI_obsolete_var BUILD_BROKEN_ENG_DEBUG_TAGS)
 $(KATI_obsolete_export It is a global setting. See $(CHANGES_URL)#export_keyword)
 $(KATI_obsolete_var BUILD_BROKEN_ANDROIDMK_EXPORTS)
+$(KATI_obsolete_var PRODUCT_STATIC_BOOT_CONTROL_HAL,Use shared library module instead. See $(CHANGES_URL)#PRODUCT_STATIC_BOOT_CONTROL_HAL)
 
 # Used to force goals to build.  Only use for conditionally defined goals.
 .PHONY: FORCE