diff --git a/libraries/AP_Terrain/AP_Terrain.cpp b/libraries/AP_Terrain/AP_Terrain.cpp
index 0b21a01027..a97eb18a36 100644
--- a/libraries/AP_Terrain/AP_Terrain.cpp
+++ b/libraries/AP_Terrain/AP_Terrain.cpp
@@ -58,7 +58,6 @@ AP_Terrain::AP_Terrain(AP_AHRS &_ahrs, const AP_Mission &_mission, const AP_Rall
     mission(_mission),
     rally(_rally),
     disk_io_state(DiskIoIdle),
-    last_request_time_ms(0),
     fd(-1),
     timer_setup(false),
     file_lat_degrees(0),
@@ -72,6 +71,7 @@ AP_Terrain::AP_Terrain(AP_AHRS &_ahrs, const AP_Mission &_mission, const AP_Rall
     AP_Param::setup_object_defaults(this, var_info);
     memset(&home_loc, 0, sizeof(home_loc));
     memset(&disk_block, 0, sizeof(disk_block));
+    memset(last_request_time_ms, 0, sizeof(last_request_time_ms));
 }
 
 /*
diff --git a/libraries/AP_Terrain/AP_Terrain.h b/libraries/AP_Terrain/AP_Terrain.h
index df81003c53..ba503a6458 100644
--- a/libraries/AP_Terrain/AP_Terrain.h
+++ b/libraries/AP_Terrain/AP_Terrain.h
@@ -352,7 +352,7 @@ private:
     union grid_io_block disk_block;
 
     // last time we asked for more grids
-    uint32_t last_request_time_ms;
+    uint32_t last_request_time_ms[MAVLINK_COMM_NUM_BUFFERS];
 
     static const uint64_t bitmap_mask = (((uint64_t)1U)<<(TERRAIN_GRID_BLOCK_MUL_X*TERRAIN_GRID_BLOCK_MUL_Y)) - 1;
 
diff --git a/libraries/AP_Terrain/TerrainGCS.cpp b/libraries/AP_Terrain/TerrainGCS.cpp
index 56403894c7..73e32f7cab 100644
--- a/libraries/AP_Terrain/TerrainGCS.cpp
+++ b/libraries/AP_Terrain/TerrainGCS.cpp
@@ -64,7 +64,7 @@ bool AP_Terrain::request_missing(mavlink_channel_t chan, struct grid_cache &gcac
       ask the GCS to send a set of 4x4 grids
      */
     mavlink_msg_terrain_request_send(chan, grid.lat, grid.lon, grid_spacing, bitmap_mask & ~grid.bitmap);
-    last_request_time_ms = hal.scheduler->millis();
+    last_request_time_ms[chan] = hal.scheduler->millis();
 
     return true;
 }
@@ -102,7 +102,7 @@ void AP_Terrain::send_request(mavlink_channel_t chan)
     send_terrain_report(chan, loc, true);
 
     // did we request recently?
-    if (hal.scheduler->millis() - last_request_time_ms < 2000) {
+    if (hal.scheduler->millis() - last_request_time_ms[chan] < 2000) {
         // too soon to request again
         return;
     }