diff --git a/cartridge/failover.lua b/cartridge/failover.lua
index fcb1f3fe9..d908c3f0b 100644
--- a/cartridge/failover.lua
+++ b/cartridge/failover.lua
@@ -432,7 +432,7 @@ local function synchro_promote()
         local ok, err = pcall(box.ctl.promote)
         fiber.testcancel()
         if ok ~= true then
-            log.error('Failed to promote: %s', err)
+            log.error('Failed to promote: %s', err or 'unknown')
         end
         return err
     end
@@ -448,7 +448,7 @@ local function synchro_demote()
         local ok, err = pcall(box.ctl.demote)
         fiber.testcancel()
         if ok ~= true then
-            log.error('Failed to demote: %s', err)
+            log.error('Failed to demote: %s', err or 'unknown')
         end
         return err
     end
diff --git a/cartridge/failover/raft.lua b/cartridge/failover/raft.lua
index 37f2dbe18..a1b4570e4 100644
--- a/cartridge/failover/raft.lua
+++ b/cartridge/failover/raft.lua
@@ -150,9 +150,9 @@ local function disable()
     and box_info.synchro.queue ~= nil
     and box_info.synchro.queue.owner ~= 0
     and box_info.synchro.queue.owner == box_info.id then
-        local err = pcall(box.ctl.demote)
-        if err ~= nil then
-            log.error('Failed to demote: %s', err)
+        local ok, err = pcall(box.ctl.demote)
+        if ok ~= true then
+            log.error('Failed to demote: %s', err or 'unknown')
         end
         return err
     end