diff --git a/radio/src/CMakeLists.txt b/radio/src/CMakeLists.txt
index e34b07ec6..23e4b648b 100644
--- a/radio/src/CMakeLists.txt
+++ b/radio/src/CMakeLists.txt
@@ -44,6 +44,7 @@ option(TRACE_LUA_INTERNALS "Turn on traces for Lua internals" OFF)
 option(BINDING_OPTIONS "Allow advanced frsky bindings" OFF)
 option(FRSKY_STICKS "Reverse sticks for FrSky sticks" OFF)
 option(NANO "Use nano newlib and binalloc")
+option(NIGHTLY_BUILD_WARNING "Warn this is a nightly build" OFF)
 
 # since we reset all default CMAKE compiler flags for firmware builds, provide an alternate way for user to specify additional flags.
 set(FIRMWARE_C_FLAGS "" CACHE STRING "Additional flags for firmware target c compiler (note: all CMAKE_C_FLAGS[_*] are ignored for firmware/bootloader).")
@@ -347,6 +348,10 @@ if(EEPROM_VARIANT_NEEDED)
   add_definitions(-DEEPROM_VARIANT=${EEPROM_VARIANT})
 endif()
 
+if(NIGHTLY_BUILD_WARNING)
+  add_definitions(-DNIGHTLY_BUILD_WARNING)
+endif(NIGHTLY_BUILD_WARNING)
+
 set(SRC
   ${SRC}
   opentx.cpp
@@ -486,7 +491,7 @@ if(NOT MSVC)
       set(SRC ${SRC} bin_allocator.cpp)
     endif()
 
-    
+
     if(PCB STREQUAL X9D OR PCB STREQUAL X9D+ OR PCB STREQUAL X9E OR PCB STREQUAL X7 OR PCB STREQUAL X7S)
       add_subdirectory(targets/${TARGET_DIR}/bootloader)
       include_directories(${CMAKE_CURRENT_BINARY_DIR}/targets/${TARGET_DIR}/bootloader)
diff --git a/radio/src/opentx.cpp b/radio/src/opentx.cpp
index fa0979d21..d347b8a7c 100644
--- a/radio/src/opentx.cpp
+++ b/radio/src/opentx.cpp
@@ -1911,6 +1911,10 @@ void opentxStart(OPENTX_START_ARGS)
   }
 #endif
 
+#if defined(NIGHTLY_BUILD_WARNING)
+  ALERT("NIGHTLY", "Version not safe to fly", AU_ERROR);
+#endif
+
 #if defined(GUI)
   if (calibration_needed) {
     chainMenu(menuFirstCalib);
diff --git a/tools/build-companion-nightly.sh b/tools/build-companion-nightly.sh
index 998d073b3..a205b9fb6 100755
--- a/tools/build-companion-nightly.sh
+++ b/tools/build-companion-nightly.sh
@@ -25,7 +25,7 @@ done
 SRCDIR=$1
 OUTDIR=$2
 
-COMMON_OPTIONS="-DALLOW_NIGHTLY_BUILDS=YES -DGVARS=YES -DHELI=YES -DLUA=YES -DMULTIMODULE=YES -DTELEMETRY=FRSKY -DPPM_LIMITS_SYMETRICAL=YES -DVARIO=YES -DGAUGES=YES -DAUTOSWITCH=YES -DAUTOSOURCE=YES -DAUDIO=YES -DGPS=YES -DPPM_CENTER_ADJUSTABLE=YES -DFLIGHT_MODES=YES -DOVERRIDE_CHANNEL_FUNCTION=YES -DFRSKY_STICKS=YES"
+COMMON_OPTIONS="-DALLOW_NIGHTLY_BUILDS=YES -DNIGHTLY_BUILD_WARNING=YES -DGVARS=YES -DHELI=YES -DLUA=YES -DMULTIMODULE=YES -DTELEMETRY=FRSKY -DPPM_LIMITS_SYMETRICAL=YES -DVARIO=YES -DGAUGES=YES -DAUTOSWITCH=YES -DAUTOSOURCE=YES -DAUDIO=YES -DGPS=YES -DPPM_CENTER_ADJUSTABLE=YES -DFLIGHT_MODES=YES -DOVERRIDE_CHANNEL_FUNCTION=YES -DFRSKY_STICKS=YES"
 if [ "$(uname)" = "Darwin" ]; then
     COMMON_OPTIONS="${COMMON_OPTIONS} -DCMAKE_PREFIX_PATH=~/Qt/5.7/clang_64/ -DCMAKE_OSX_DEPLOYMENT_TARGET='10.9'"
 fi