diff --git a/src/core/mac/mac.cpp b/src/core/mac/mac.cpp
index c6f5da24f..4ff0a0e7b 100644
--- a/src/core/mac/mac.cpp
+++ b/src/core/mac/mac.cpp
@@ -234,8 +234,8 @@ otError Mac::ConvertBeaconToActiveScanResult(Frame *aBeaconFrame, otActiveScanRe
         aResult.mVersion    = beaconPayload->GetProtocolVersion();
         aResult.mIsJoinable = beaconPayload->IsJoiningPermitted();
         aResult.mIsNative   = beaconPayload->IsNative();
-        memcpy(&aResult.mNetworkName, beaconPayload->GetNetworkName(), sizeof(aResult.mNetworkName));
-        memcpy(&aResult.mExtendedPanId, beaconPayload->GetExtendedPanId(), sizeof(aResult.mExtendedPanId));
+        memcpy(&aResult.mNetworkName, beaconPayload->GetNetworkName(), BeaconPayload::kNetworkNameSize);
+        memcpy(&aResult.mExtendedPanId, beaconPayload->GetExtendedPanId(), BeaconPayload::kExtPanIdSize);
     }
 
     LogBeacon("Received", *beaconPayload);