diff --git a/libraries/DataFlash/DataFlash.cpp b/libraries/DataFlash/DataFlash.cpp
index 70040b4959e55..4fb81123f0742 100644
--- a/libraries/DataFlash/DataFlash.cpp
+++ b/libraries/DataFlash/DataFlash.cpp
@@ -265,6 +265,19 @@ void DataFlash_Class::Log_Write_MessageF(const char *fmt, ...)
     Log_Write_Message(msg);
 }
 
+void DataFlash_Class::backend_starting_new_log(const DataFlash_Backend *backend)
+{
+    for (uint8_t i=0; i<_next_backend; i++) {
+        if (backends[i] == backend) { // pointer comparison!
+            // reset sent masks
+            for (struct log_write_fmt *f = log_write_fmts; f; f=f->next) {
+                f->sent_mask &= ~(1<<i);
+            }
+            break;
+        }
+    }
+}
+
 #define FOR_EACH_BACKEND(methodcall)              \
     do {                                          \
         for (uint8_t i=0; i<_next_backend; i++) { \
diff --git a/libraries/DataFlash/DataFlash.h b/libraries/DataFlash/DataFlash.h
index df57efe876f70..3ff02115701d1 100644
--- a/libraries/DataFlash/DataFlash.h
+++ b/libraries/DataFlash/DataFlash.h
@@ -272,7 +272,9 @@ class DataFlash_Class
     void Log_Write_EKF2(AP_AHRS_NavEKF &ahrs, bool optFlowEnabled);
     void Log_Write_EKF3(AP_AHRS_NavEKF &ahrs, bool optFlowEnabled);
 #endif
-    
+
+    void backend_starting_new_log(const DataFlash_Backend *backend);
+
 private:
     static DataFlash_Class *_instance;
 
diff --git a/libraries/DataFlash/DataFlash_Backend.cpp b/libraries/DataFlash/DataFlash_Backend.cpp
index f9a8a7e763177..bffd9f3296ba6 100644
--- a/libraries/DataFlash/DataFlash_Backend.cpp
+++ b/libraries/DataFlash/DataFlash_Backend.cpp
@@ -53,6 +53,7 @@ void DataFlash_Backend::periodic_tasks()
 void DataFlash_Backend::start_new_log_reset_variables()
 {
     _startup_messagewriter->reset();
+    _front.backend_starting_new_log(this);
 }
 
 void DataFlash_Backend::internal_error() {
diff --git a/libraries/DataFlash/LogFile.cpp b/libraries/DataFlash/LogFile.cpp
index 1606d0b9402ab..07ea2bce4936e 100644
--- a/libraries/DataFlash/LogFile.cpp
+++ b/libraries/DataFlash/LogFile.cpp
@@ -584,15 +584,14 @@ void DataFlash_Block::ListAvailableLogs(AP_HAL::BetterStream *port)
 
 // This function starts a new log file in the DataFlash, and writes
 // the format of supported messages in the log
+// This function is ONLY called from the vehicle code.
+// DataFlash_MAVLink, for example, will NOT call this function if the
+// remote end disconnects and reconnects!
 void DataFlash_Class::StartNewLog(void)
 {
     for (uint8_t i=0; i<_next_backend; i++) {
         backends[i]->start_new_log();
     }
-    // reset sent masks
-    for (struct log_write_fmt *f = log_write_fmts; f; f=f->next) {
-        f->sent_mask = 0;
-    }
 }
 
 /*