diff --git a/process_maps.py b/process_maps.py
index 08da07c..d6cacc7 100755
--- a/process_maps.py
+++ b/process_maps.py
@@ -32,6 +32,8 @@ if __name__ == '__main__':
                         help='don\'t sleep between downloads -- WARNING you can easily run into throttling on mirrors if you use this option')
 	parser.add_argument('--use-ram', action='store_true',
                         help='use RAM for mapsforge processing -- WARNING mapsforge uses 10x the map size in RAM for processing (ie. 100Mb map = 1Gb RAM usage), you want a LOT of RAM for this option')
+	parser.add_argument('--max-heap-space', action='store', default='4g',
+                        help='set the max heap space for the JVM, use standard -Xmx values, default (4g) should be fine if not using --use-ram argument')
 	#TODO: Add argument to pass path to osmosis
 	#TODO: Add argument to pass path to output dir
 	args = parser.parse_args()
@@ -72,7 +74,7 @@ if __name__ == '__main__':
 				subprocess.run([bunzip2_cmd, os.path.join(dirpath, file)])
 				
 	# Setup various runtime aspects (going to do multiple osmosis runs (maps AND POIs)
-	env['JAVACMD_OPTIONS'] = '-server -Djava.io.tmpdir=' + os.path.join(base_path, 'tmp') # Setup java temp dir to something a bit more sane (tmpfs /tmp for the loss)
+	env['JAVACMD_OPTIONS'] = '-Xmx' + args.max_heap_space + ' -server -Djava.io.tmpdir=' + os.path.join(base_path, 'tmp') # Setup java temp dir to something a bit more sane (tmpfs /tmp for the loss)
 	files_to_process = []
 	for dirpath, dirnames, filenames in os.walk('dl'):
 		for file in filenames: