diff --git a/app/overlays/ptl/ll_userspace_overlay.conf b/app/overlays/ptl/ll_userspace_overlay.conf
index 53b881320e6f..0de9a6e9913c 100644
--- a/app/overlays/ptl/ll_userspace_overlay.conf
+++ b/app/overlays/ptl/ll_userspace_overlay.conf
@@ -37,3 +37,9 @@ CONFIG_CROSS_CORE_STREAM=n
 CONFIG_INTEL_ADSP_MIC_PRIVACY=n
 CONFIG_XRUN_NOTIFICATIONS_ENABLE=n
 CONFIG_ZEPHYR_DP_SCHEDULER=n
+
+# Extend the shared LL user-space heap to 512KiB. This
+# is current maximum for PTL builds with virtual heap
+# enabled and uses the vmh allocation intended for KBP.
+# TODO: needs some better solution to allocate
+CONFIG_SOF_ZEPHYR_SYS_USER_HEAP_SIZE=0x80000