diff --git a/shell/i.cpp b/shell/i.cpp
index aff5642..6c04ecc 100644
--- a/shell/i.cpp
+++ b/shell/i.cpp
@@ -140,16 +140,14 @@ struct _isc_args
 
 static struct _isc_args parse_isc(Session &, Parser &parser)
 {
-    struct _isc_args args
-    {
-    };
+    _isc_args args;
 
     parser.option("sort",
         [&args](std::string const &value) { args.sort = (value == "true"); });
+    parser.option("vspace",
+        [&args](std::string const &value) { args.vspace_name = value; });
 
     parser.accept_options();
-    args.vspace_name = parser.at_end() ? "" : parser.symbol("vspace_name");
-    parser.accept_options();
 
     parser.end();
     return args;
@@ -169,16 +167,18 @@ bool operator<(const SyscallInfo &left, const SyscallInfo &right)
 void _isc(Session &session, std::string vspace_name, bool sort)
 {
     VirtualSpace *space = session.current_space;
-    if(vspace_name != "")
+    if(!vspace_name.empty())
         space = session.get_space(vspace_name);
-    if(!space)
-        return;
 
-    // TODO: is <vspace_name> doesn't work
+    if(!space)
+        throw CommandError("virtual space '{}' does not exist", vspace_name);
 
     OS *os = space->os_analysis();
-    if(!os)
-        throw CommandError("os analysis on '{}' failed", vspace_name);
+    if(!os) {
+        if (!vspace_name.empty())
+            throw CommandError("OS analysis on '{}' failed", vspace_name);
+        throw CommandError("OS analysis failed");
+    }
 
     int total = os->syscall_count();
     auto info = std::make_unique<SyscallInfo[]>(total);
@@ -257,7 +257,7 @@ static ShellCommand _isc_cmd(
         _isc(s, args.vspace_name, args.sort);
     },
     [](Session &s, Parser &p) { parse_isc(s, p); }, "Info Syscalls", R"(
-isc [sort=true] [<vspace_name>]
+isc [sort=true] [vspace=<virtual_name>]
 
 Prints the syscall table for the specified virtual space (defaults to the
 current one). By default, syscalls are enumerated by syscall number. If