diff --git a/samples/cellular/lwm2m_client/overlay-assist-cell.conf b/samples/cellular/lwm2m_client/overlay-assist-cell.conf
index 30d56c24513c..177ed5fb5292 100644
--- a/samples/cellular/lwm2m_client/overlay-assist-cell.conf
+++ b/samples/cellular/lwm2m_client/overlay-assist-cell.conf
@@ -11,8 +11,6 @@ CONFIG_LWM2M_RW_SENML_CBOR_SUPPORT=y
 CONFIG_ZCBOR=y
 CONFIG_ZCBOR_CANONICAL=y
 CONFIG_LWM2M_RW_SENML_CBOR_RECORDS=35
-# Increase AT monitor heap because %NCELLMEAS notifications can be large
-CONFIG_AT_MONITOR_HEAP_SIZE=512
 
 # AVSystem CDM-665 workaround: force object version reporting.
 CONFIG_LWM2M_CONNMON_OBJECT_VERSION_1_3=y
diff --git a/samples/cellular/lwm2m_client/prj.conf b/samples/cellular/lwm2m_client/prj.conf
index 686e97b7fbaa..800cf3aa8054 100644
--- a/samples/cellular/lwm2m_client/prj.conf
+++ b/samples/cellular/lwm2m_client/prj.conf
@@ -76,6 +76,7 @@ CONFIG_HEAP_MEM_POOL_SIZE=16384
 CONFIG_MAIN_STACK_SIZE=4096
 CONFIG_LWM2M_ENGINE_STACK_SIZE=3072
 CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048
+CONFIG_AT_MONITOR_HEAP_SIZE=512
 
 # Allow FOTA downloads using download-client
 CONFIG_DOWNLOAD_CLIENT=y