diff --git i/lib/redmine/thumbnail.rb w/lib/redmine/thumbnail.rb
index 91d6a6fed..2d6f384a3 100644
--- i/lib/redmine/thumbnail.rb
+++ w/lib/redmine/thumbnail.rb
@@ -24,7 +24,15 @@ module Redmine
   module Thumbnail
     extend Redmine::Utils::Shell
 
-    CONVERT_BIN = (Redmine::Configuration['imagemagick_convert_command'] || 'convert').freeze
+    CONVERT_BIN = (
+      Redmine::Configuration['imagemagick_convert_command'] ||
+      begin
+        `magick --version`
+        $?.success? ? 'magick' : 'convert'
+      rescue
+        'convert'
+      end
+    ).freeze
     GS_BIN = (
       Redmine::Configuration['gs_command'] ||
       ('gswin64c' if Redmine::Platform.mswin?) ||