diff --git a/src/open9x.cpp b/src/open9x.cpp
index 611770e53..cbdd81df4 100644
--- a/src/open9x.cpp
+++ b/src/open9x.cpp
@@ -62,6 +62,7 @@ OS_STK debugStack[DEBUG_STACK_SIZE];
 OS_TCID audioTimer;
 OS_FlagID audioFlag;
 
+OS_MutexID sdMutex;
 OS_MutexID audioMutex;
 OS_MutexID mixerMutex;
 #endif
@@ -3595,6 +3596,7 @@ int main(void)
   audioTimer = CoCreateTmr(TMR_TYPE_ONE_SHOT, 1000/(1000/CFG_SYSTICK_FREQ), 1000/(1000/CFG_SYSTICK_FREQ), audioTimerHandle);
   audioTaskId = CoCreateTask(audioTask, NULL, 7, &audioStack[AUDIO_STACK_SIZE-1], AUDIO_STACK_SIZE);
 
+  sdMutex = CoCreateMutex();
   audioMutex = CoCreateMutex();
   mixerMutex = CoCreateMutex();