diff --git a/DMRTX.cpp b/DMRTX.cpp
index abf9331..e99d1a0 100644
--- a/DMRTX.cpp
+++ b/DMRTX.cpp
@@ -255,14 +255,20 @@ void CDMRTX::createData(uint8_t slotIndex)
   if (m_fifo[slotIndex].getData() > 0U && m_frameCount >= STARTUP_COUNT) {
     for (unsigned int i = 0U; i < DMR_FRAME_LENGTH_BYTES; i++) {
       m_poBuffer[i]   = m_fifo[slotIndex].get();
-      m_markBuffer[i] = MARK_NONE;
+      if (i == 8U)
+        m_markBuffer[i] = slotIndex == 0U ? MARK_SLOT1 : MARK_SLOT2;
+      else
+        m_markBuffer[i] = MARK_NONE;
     }
   } else {
     m_abort[slotIndex] = false;
     // Transmit an idle message
     for (unsigned int i = 0U; i < DMR_FRAME_LENGTH_BYTES; i++) {
       m_poBuffer[i]   = m_idle[i];
-      m_markBuffer[i] = MARK_NONE;
+      if (i == 8U)
+        m_markBuffer[i] = slotIndex == 0U ? MARK_SLOT1 : MARK_SLOT2;
+      else
+        m_markBuffer[i] = MARK_NONE;
     }
   }
 
@@ -287,7 +293,7 @@ void CDMRTX::createCACH(uint8_t txSlotIndex, uint8_t rxSlotIndex)
   ::memcpy(m_poBuffer, m_shortLC + m_cachPtr, 3U);
   m_markBuffer[0U] = MARK_NONE;
   m_markBuffer[1U] = MARK_NONE;
-  m_markBuffer[2U] = rxSlotIndex == 1U ? MARK_SLOT1 : MARK_SLOT2;
+  m_markBuffer[2U] = MARK_NONE;
 
   bool at = false;
   if (m_frameCount >= STARTUP_COUNT)
diff --git a/README.md b/README.md
index 3554997..a8280f9 100644
--- a/README.md
+++ b/README.md
@@ -107,7 +107,7 @@ and wait to complete the upgrading process.
 
 You could use example files from MMDVM_HS/configs folder and overwrite the Config.h file, in order to compile a firmware with default settings. There are a specific config file for each ZUMspot or any MMDVM_HS compatible boards. In general, there are two possible compilation ways:
 
-- Board with USB interface
+- Boards with USB interface:
 
 Boards with STM32_USB_HOST option enabled in Config.h (ZUMspot Libre Kit, ZUMspot USB, GIBSpot USB, NanoDV USB, etc). Those boards need to have the USB bootloader installed. For example:
 
@@ -115,7 +115,7 @@ Boards with STM32_USB_HOST option enabled in Config.h (ZUMspot Libre Kit, ZUMspo
     make bl
     make dfu
 
-- Board with GPIO interface
+- Boards with GPIO interface:
 
 Boards with STM32_USART1_HOST option enabled in Config.h (ZUMspot RPi, MMDVM_HS_Hat, MMDVM_HS_Dual_Hat, Nano hotSPOT, etc). No USB bootloader needed. For example: