diff --git a/BPTC19696.cpp b/BPTC19696.cpp
index 7fbddef..6f42b34 100644
--- a/BPTC19696.cpp
+++ b/BPTC19696.cpp
@@ -328,7 +328,7 @@ void CBPTC19696::encodeExtractBinary(unsigned char* data)
 	unsigned char byte;
 	CUtils::bitsToByteBE(m_rawData + 96U, byte);
 	data[12U] = (data[12U] & 0x3FU) | ((byte >> 0) & 0xC0U);
-	data[13U] = (data[13U] & 0xFCU) | ((byte >> 4) & 0x03U);
+	data[20U] = (data[20U] & 0xFCU) | ((byte >> 4) & 0x03U);
 
 // Second block
 	CUtils::bitsToByteBE(m_rawData + 100U,  data[21U]);