When you went "losetup -d /dev/loop0 /dev/loop1" the error message was strange.

2 files changed, 3 insertions, 2 deletions

diff --git a/include/usage.h b/include/usage.h
index 12c45b45f..9de9df8f3 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -1657,7 +1657,7 @@
         "\t-f\t\toutput data as the log grows"
 
 #define losetup_trivial_usage \
-        "[-od] LOOPDEVICE [FILE]\n"
+        "[-od] LOOPDEVICE [FILE]"
 #define losetup_full_usage \
         "Associate LOOPDEVICE with FILE, or display current association.\n\n" \
         "Options:\n" \
diff --git a/util-linux/losetup.c b/util-linux/losetup.c
index b2af63dc0..44721bd34 100644
--- a/util-linux/losetup.c
+++ b/util-linux/losetup.c
@@ -33,7 +33,8 @@ int losetup_main (int argc, char **argv)
   switch(getopt(argc,argv, "do:")) {
     case 'd':
       /* detach takes exactly one argument */
-      if(optind+1==argc && !del_loop(argv[optind])) return EXIT_SUCCESS;
+      if(optind+1!=argc) bb_show_usage();
+      if(!del_loop(argv[optind])) return EXIT_SUCCESS;
 die_failed:
       bb_perror_msg_and_die("%s",argv[optind]);