diff --git a/lib/redmine/thumbnail.rb b/lib/redmine/thumbnail.rb
index a46a09ee1..31ac62272 100644
--- a/lib/redmine/thumbnail.rb
+++ b/lib/redmine/thumbnail.rb
@@ -51,7 +51,12 @@ module Redmine
 
     def self.convert_available?
       return @convert_available if defined?(@convert_available)
-      @convert_available = system("#{shell_quote CONVERT_BIN} -version") rescue false
+      begin
+        `#{shell_quote CONVERT_BIN} -version`
+        @convert_available = $?.success?
+      rescue
+        @convert_available = false
+      end
       logger.warn("Imagemagick's convert binary (#{CONVERT_BIN}) not available") unless @convert_available
       @convert_available
     end