diff --git a/blocksfree/legacy.py b/blocksfree/legacy.py
index 82d479c..0d04a52 100755
--- a/blocksfree/legacy.py
+++ b/blocksfree/legacy.py
@@ -87,6 +87,7 @@ g.DIRPATH = ""
 g.target_name = None
 g.target_dir = ""
 g.appledouble_dir = None
+g.image_file = None
 g.extract_file = None
 
 # runtime options
@@ -1030,7 +1031,7 @@ def hexdump(
 
 def run_cppo(args: list):
 	try:
-		disk = Disk(args[1])
+		disk = Disk(g.image_file)
 	except IOError as e:
 		log.critical(e)
 		quit_now(2)
@@ -1051,24 +1052,6 @@ def run_cppo(args: list):
 						"ShrinkIt archive.")
 				quit_now(2)
 
-	if len(args) == 4:
-		g.extract_file = args[2]
-
-	if g.extract_file:
-		targetPath = args[3]
-		if os.path.isdir(targetPath):
-			g.target_dir = targetPath
-		elif len(targetPath.rsplit("/", 1)) > 1:
-			g.target_dir, g.target_name = targetPath.rsplit("/", 1)
-		if not os.path.isdir(g.target_dir):
-			print("Target directory {} not found.".format(g.target_dir))
-			quit_now(2)
-	else:
-		if not g.catalog_only:
-			if not os.path.isdir(args[2]):
-				print("Target directory not found.")
-				quit_now(2)
-
 	if g.src_shk:
 		g.prodos_names = False
 		if not g.catalog_only:
@@ -1222,7 +1205,8 @@ def run_cppo(args: list):
 	if (not g.src_shk and not g.dos33 and g.extract_file
 			and (args[2][0] not in ('/', ':'))):
 		log.critical("Cannot extract {} from {}: "
-				"ProDOS volume name required".format(args[2], args[1]))
+				"ProDOS volume name required".format(
+					g.extract_file, g.image_file))
 		quit_now(2)
 
 	if g.dos33:
diff --git a/cppo b/cppo
index 8ab1b93..293391e 100755
--- a/cppo
+++ b/cppo
@@ -45,6 +45,7 @@ Wildcard matching (*) is not supported and images are not validated.
 ShrinkIt support requires Nulib2. cppo requires Python 2.6+ or 3.0+."""
 
 import sys
+import os
 
 from blocksfree.legacy import g
 import blocksfree.legacy
@@ -98,6 +99,35 @@ def cppo(args: list):
 		else:
 			usage()
 
+	if g.use_appledouble and g.use_extended:
+		usage()
+	if g.catalog_only:
+		if len(args) != 2:
+			usage()
+	else:
+		if len(args) not in (3, 4):
+			usage()
+
+	g.image_file = args[1]
+
+	if len(args) == 4:
+		g.extract_file = args[2]
+
+	if g.extract_file:
+		target_path = args[3]
+		if os.path.isdir(target_path):
+			g.target_dir = target_path
+		elif len(target_path.rsplit("/", 1)) > 1:
+			g.target_dir, g.target_name = target_path.rsplit("/", 1)
+		if not os.path.isdir(g.target_dir):
+			log.critical("Directory {} not found.".format(g.target_dir))
+			sys.exit(2)
+	else:
+		if not g.catalog_only:
+			if not os.path.isdir(args[2]):
+				log.critical("Directory {} not found.".format(g.target_dir))
+				sys.exit(2)
+
 	blocksfree.legacy.run_cppo(args)
 
 if __name__ == '__main__':