diff --git a/lisp/_prepare.lisp b/lisp/_prepare.lisp
index c70b6ad..25878fa 100644
--- a/lisp/_prepare.lisp
+++ b/lisp/_prepare.lisp
@@ -490,12 +490,6 @@ to actually set up the systems."
   (let ((path (car (cdr (qob-primary-system-entry)))))
     (qob-file-name-directory path)))
 
-(defun qob-only-system ()
-  "Return the default system if only one system is loaded in the workspace."
-  (qob-init-asds)
-  (when (= (length qob-loaded-asds) 1)
-    (qob-primary-system-entry)))
-
 (defun qob-find-asd-file (name)
   "Return the ASD file by system's NAME."
   (let ((result))
diff --git a/lisp/core/build.lisp b/lisp/core/build.lisp
index f1c2a17..776dfe9 100644
--- a/lisp/core/build.lisp
+++ b/lisp/core/build.lisp
@@ -49,21 +49,21 @@
 (qob-start
  (let* ((systems (qob-args))
         (systems-len (length systems))
-        (default-name (qob-only-system)))
+        (primary-system (qob-primary-system-entry)))
    (cond
-     ;; If only specified one system.
-     (default-name
-      (qob-build--print-header 1)
-      (qob-build--system-by-name (car default-name))
-      (qob-build--print-footer))
-     ;; If no system(s) specified.
-     ((zerop systems-len)
-      (qob-help "core/build"))
-     ;; Build system for all specify systems.
-     (t
+     ;; If specified system(s).
+     (systems
       (qob-build--print-header systems-len)
       (dolist (name systems)
         (qob-build--system-by-name name))
-      (qob-build--print-footer)))))
+      (qob-build--print-footer))
+     ;; Print primary system.
+     (primary-system
+      (qob-build--print-header 1)
+      (qob-build--system-by-name (car primary-system))
+      (qob-build--print-footer))
+     ;; Print help.
+     (t
+      (qob-help "core/build")))))
 
 ;;; End of lisp/core/build.lisp
diff --git a/lisp/core/info.lisp b/lisp/core/info.lisp
index ced2d09..444257a 100644
--- a/lisp/core/info.lisp
+++ b/lisp/core/info.lisp
@@ -54,17 +54,17 @@
 
 (qob-start
  (let ((names (qob-args))
-       (default-system (qob-only-system)))
+       (primary-system (qob-primary-system-entry)))
    (cond
-     ;; If only specified one system.
-     (default-system
-      (qob-info--print-system (car default-system)))
-     ;; If no system(s) specified.
-     ((zerop (length names))
-      (qob-help "core/info"))
-     ;; Print all systems information.
-     (t
+     ;; If specified system(s).
+     (names
       (dolist (name names)
-        (qob-info--print-system name))))))
+        (qob-info--print-system name)))
+     ;; Print primary system.
+     (primary-system
+      (qob-info--print-system (car primary-system)))
+     ;; Print help.
+     (t
+      (qob-help "core/info")))))
 
 ;;; End of lisp/core/info.lisp
diff --git a/lisp/core/install-deps.lisp b/lisp/core/install-deps.lisp
index 3d7c6ac..514b913 100644
--- a/lisp/core/install-deps.lisp
+++ b/lisp/core/install-deps.lisp
@@ -57,17 +57,17 @@
 
 (qob-start
  (let ((systems (qob-args))
-       (default-name (qob-only-system)))
+       (primary-system (qob-primary-system-entry)))
    (cond
-     ;; If only specified one system.
-     (default-name
-      (qob-install-deps--by-system-name (car default-name)))
-     ;; If no system(s) specified.
-     ((zerop (length systems))
-      (qob-help "core/install-deps"))
-     ;; Install depedencies for all specify systems.
-     (t
+     ;; If specified system(s).
+     (systems
       (dolist (system-name systems)
-        (qob-install-deps--by-system-name system-name))))))
+        (qob-install-deps--by-system-name system-name)))
+     ;; Print primary system.
+     (primary-system
+      (qob-install-deps--by-system-name (car primary-system)))
+     ;; Print help.
+     (t
+      (qob-help "core/install-deps")))))
 
 ;;; End of lisp/core/install-deps.lisp