diff --git a/radio/src/gui/gui_common_arm.cpp b/radio/src/gui/gui_common_arm.cpp
index 8c38b03f2..0355166d0 100644
--- a/radio/src/gui/gui_common_arm.cpp
+++ b/radio/src/gui/gui_common_arm.cpp
@@ -544,7 +544,7 @@ bool isExternalModuleAvailable(int module)
   }
 #endif
 #if !defined(PXX2)
-  if (module == MODULE_TYPE_XJT2) {
+  if (module == MODULE_TYPE_XJT2 || module == MODULE_TYPE_R9M2) {
     return false;
   }
 #endif
diff --git a/radio/src/io/frsky_pxx2.h b/radio/src/io/frsky_pxx2.h
index b879ebec6..560ae2b9b 100644
--- a/radio/src/io/frsky_pxx2.h
+++ b/radio/src/io/frsky_pxx2.h
@@ -25,8 +25,9 @@
 
 #define PXX2_BAUDRATE            230400
 #define PXX2_PERIOD              4 // 4ms
+#define PXX2_FRAME_MAXLENGTH     32
 
-class ModuleFifo : public Fifo<uint8_t, 32> {
+class ModuleFifo : public Fifo<uint8_t, PXX2_FRAME_MAXLENGTH> {
   public:
     bool getFrame(uint8_t * frame)
     {
@@ -45,6 +46,7 @@ class ModuleFifo : public Fifo<uint8_t, 32> {
       uint32_t next = nextIndex(ridx);
       uint8_t len = fifo[next];
       if (unsigned(len + 4 /* 2 bytes header + 2 bytes CRC */) > size()) {
+        // frame not fully received
         return false;
       }
 
diff --git a/radio/src/telemetry/telemetry.cpp b/radio/src/telemetry/telemetry.cpp
index b1de783c9..737e22a80 100644
--- a/radio/src/telemetry/telemetry.cpp
+++ b/radio/src/telemetry/telemetry.cpp
@@ -211,7 +211,7 @@ void telemetryWakeup()
 #endif
 
 #if defined(INTMODULE_USART) || defined(EXTMODULE_USART)
-  uint8_t frame[32];
+  uint8_t frame[PXX2_FRAME_MAXLENGTH];
 
   #if defined(INTMODULE_USART)
     if (intmoduleFifo.getFrame(frame)) {