diff --git a/cl-gpu.asd b/cl-gpu.asd
index 1a55bff..62d9b7e 100644
--- a/cl-gpu.asd
+++ b/cl-gpu.asd
@@ -6,18 +6,17 @@
 
 ;; Auto-detect CUDA
 #-(or cuda (and ecl (not (and dffi dlopen))))
-(load-system :cffi)
+(load-system "cffi")
 
 #-(or cuda (and ecl (not (and dffi dlopen))))
 (when (ignore-errors (cffi:load-foreign-library '(:default "libcuda")) t)
   (pushnew :cuda *features*))
 
-;; System definition
-(defsystem :cl-gpu
-  :defsystem-depends-on (:hu.dwim.asdf)
+(defsystem "cl-gpu"
+  :defsystem-depends-on ("hu.dwim.asdf")
   :class "hu.dwim.asdf:hu.dwim.system"
   :author ("Alexander Gavrilov <angavrilov@gmail.com>")
   :licence "LLGPL"
   :description "A library for writing GPU kernels in a subset of CL"
-  :depends-on (:cl-gpu.core
-               #+cuda :cl-gpu.cuda))
+  :depends-on ("cl-gpu.core"
+               #+cuda "cl-gpu.cuda"))
diff --git a/cl-gpu.buffers.asd b/cl-gpu.buffers.asd
index 33ca08b..b0e15a2 100644
--- a/cl-gpu.buffers.asd
+++ b/cl-gpu.buffers.asd
@@ -4,17 +4,17 @@
 ;;;
 ;;; See LICENCE for details.
 
-(defsystem :cl-gpu.buffers
-  :defsystem-depends-on (:hu.dwim.asdf)
+(defsystem "cl-gpu.buffers"
+  :defsystem-depends-on ("hu.dwim.asdf")
   :class "hu.dwim.asdf:hu.dwim.system"
   :author ("Alexander Gavrilov <angavrilov@gmail.com>")
   :licence "LLGPL"
   :description "A helper library that provides a generalized buffer interface."
-  :depends-on (:cffi
-               #+sbcl :sb-vector-io
-               :hu.dwim.util
-               :hu.dwim.def+contextl
-               :trivial-garbage)
+  :depends-on ("cffi"
+               #+sbcl "sb-vector-io"
+               "hu.dwim.util"
+               "hu.dwim.def+contextl"
+               "trivial-garbage")
   :components ((:module "buffers"
                 :components ((:file "package")
                              (:file "utils" :depends-on ("package"))
diff --git a/cl-gpu.core.asd b/cl-gpu.core.asd
index 9fd0934..000ed6d 100644
--- a/cl-gpu.core.asd
+++ b/cl-gpu.core.asd
@@ -4,8 +4,8 @@
 ;;;
 ;;; See LICENCE for details.
 
-(defsystem :cl-gpu.core
-  :defsystem-depends-on (:hu.dwim.asdf)
+(defsystem "cl-gpu.core"
+  :defsystem-depends-on ("hu.dwim.asdf")
   :class "hu.dwim.asdf:hu.dwim.system"
   :author ("Alexander Gavrilov <angavrilov@gmail.com>")
   :licence "LLGPL"
diff --git a/cl-gpu.cuda.asd b/cl-gpu.cuda.asd
index 8e09189..973f6c8 100644
--- a/cl-gpu.cuda.asd
+++ b/cl-gpu.cuda.asd
@@ -4,13 +4,13 @@
 ;;;
 ;;; See LICENCE for details.
 
-(defsystem :cl-gpu.cuda
-  :defsystem-depends-on (:hu.dwim.asdf)
+(defsystem "cl-gpu.cuda"
+  :defsystem-depends-on ("hu.dwim.asdf")
   :class "hu.dwim.asdf:hu.dwim.system"
   :author ("Alexander Gavrilov <angavrilov@gmail.com>")
   :licence "LLGPL"
   :description "CUDA integration for the GPU code translator."
-  :depends-on (:cl-gpu.core)
+  :depends-on ("cl-gpu.core")
   :components ((:module "cuda"
                 :components ((:file "driver-lib")
                              (:file "driver-api" :depends-on ("driver-lib"))
@@ -18,7 +18,5 @@
                              (:file "device-mem" :depends-on ("driver-api" "pitched-copy"))
                              (:file "nvcc")
                              (:file "target" :depends-on ("driver-api" "nvcc"))
-                             (:file "module" :depends-on ("device-mem" "target" "nvcc"))))))
-
-(defmethod perform :after ((o load-op) (c (eql (find-system :cl-gpu.cuda))))
-  (pushnew :cuda *features*))
+                             (:file "module" :depends-on ("device-mem" "target" "nvcc")))))
+  :perform (load-op :after (o c) (pushnew :cuda *features*)))
diff --git a/cl-gpu.test.asd b/cl-gpu.test.asd
index e249b5c..d0d06cf 100644
--- a/cl-gpu.test.asd
+++ b/cl-gpu.test.asd
@@ -4,14 +4,14 @@
 ;;;
 ;;; See LICENCE for details.
 
-(defsystem :cl-gpu.test
-  :defsystem-depends-on (:hu.dwim.asdf)
+(defsystem "cl-gpu.test"
+  :defsystem-depends-on ("hu.dwim.asdf")
   :class "hu.dwim.asdf:hu.dwim.test-system"
   :author ("Alexander Gavrilov <angavrilov@gmail.com>")
   :licence "LLGPL"
   :description "Test suite for cl-gpu"
-  :depends-on (:hu.dwim.stefil+hu.dwim.def
-               :cl-gpu)
+  :depends-on ("hu.dwim.stefil+hu.dwim.def"
+               "cl-gpu")
   :components ((:module "test"
                 :components ((:file "utils" :depends-on ("package"))
                              (:file "buffers" :depends-on ("utils"))