diff --git a/logstash-core/lib/logstash/runner.rb b/logstash-core/lib/logstash/runner.rb
index 49fc9b4e50c..3cd4a7f02e7 100644
--- a/logstash-core/lib/logstash/runner.rb
+++ b/logstash-core/lib/logstash/runner.rb
@@ -249,7 +249,9 @@ def execute
     java.lang.System.setProperty("ls.log.level", setting("log.level"))
     unless java.lang.System.getProperty("log4j.configurationFile")
       log4j_config_location = ::File.join(setting("path.settings"), "log4j2.properties")
-      LogStash::Logging::Logger::reconfigure("file:///" + log4j_config_location)
+
+      # Windows safe way to produce a file: URI.
+      LogStash::Logging::Logger::reconfigure(URI.join("file:///" + File.absolute_path(log4j_config_location)).to_s)
     end
     # override log level that may have been introduced from a custom log4j config file
     LogStash::Logging::Logger::configure_logging(setting("log.level"))