diff --git a/haskell-process.el b/haskell-process.el
index a71ff684a..534e5ea48 100644
--- a/haskell-process.el
+++ b/haskell-process.el
@@ -104,9 +104,9 @@ See `haskell-process-do-cabal' for more details."
   :type 'string)
 
 (defcustom haskell-process-type
-  'ghci
+  'auto
   "The inferior Haskell process type to use."
-  :type '(choice (const ghci) (const cabal-repl) (const cabal-dev) (const cabal-ghci))
+  :type '(choice (const auto) (const ghci) (const cabal-repl) (const cabal-dev) (const cabal-ghci))
   :group 'haskell-interactive)
 
 (defcustom haskell-process-log
@@ -507,7 +507,7 @@ for various things, but is optional."
   "Add <cabal-project-dir>/dist/build/autogen/ to the ghci search
 path. This allows modules such as 'Path_...', generated by cabal,
 to be loaded by ghci."
-  (unless (eq 'cabal-repl haskell-process-type) ;; redundant with "cabal repl"
+  (unless (eq 'cabal-repl (haskell-process-type)) ;; redundant with "cabal repl"
     (let*
         ((session       (haskell-session))
          (cabal-dir     (haskell-session-cabal-dir session))
@@ -516,6 +516,17 @@ to be loaded by ghci."
        (haskell-process)
        (format ":set -i%s" ghci-gen-dir)))))
 
+(defun haskell-process-type ()
+  "Return `haskell-process-type', or a guess if that variable is 'auto."
+  (if (eq 'auto haskell-process-type)
+      (if (locate-dominating-file default-directory
+                                  (lambda (f)
+                                    (or (string= ".cabal-sandbox" f)
+                                        (string-match-p "\\.cabal\\'" f))))
+          'cabal-repl
+        'ghci)
+    haskell-process-type))
+
 (defun haskell-process-do-cabal (command)
   "Run a Cabal command."
   (let ((process (haskell-process)))
@@ -531,7 +542,7 @@ to be loaded by ghci."
          (format haskell-process-do-cabal-format-string
                  (haskell-session-cabal-dir (car state))
                  (format "%s %s"
-                         (cl-ecase haskell-process-type
+                         (cl-ecase (haskell-process-type)
                            ('ghci haskell-process-path-cabal)
                            ('cabal-repl haskell-process-path-cabal)
                            ('cabal-ghci haskell-process-path-cabal)
@@ -574,7 +585,7 @@ to be loaded by ghci."
               (notifications-notify
                :title (format "*%s*" (haskell-session-name (car state)))
                :body msg
-               :app-name (cl-ecase haskell-process-type
+               :app-name (cl-ecase (haskell-process-type)
                            ('ghci haskell-process-path-cabal)
                            ('cabal-repl haskell-process-path-cabal)
                            ('cabal-ghci haskell-process-path-cabal)
@@ -1006,7 +1017,7 @@ now."
       (haskell-session-pwd session)
       (haskell-process-set-process
        process
-       (cl-ecase haskell-process-type
+       (cl-ecase (haskell-process-type)
          ('ghci
           (haskell-process-log
            (propertize (format "Starting inferior GHCi process %s ..."
@@ -1057,7 +1068,7 @@ now."
     (progn (set-process-sentinel (haskell-process-process process) 'haskell-process-sentinel)
            (set-process-filter (haskell-process-process process) 'haskell-process-filter))
     (haskell-process-send-startup process)
-    (unless (eq 'cabal-repl haskell-process-type) ;; "cabal repl" sets the proper CWD
+    (unless (eq 'cabal-repl (haskell-process-type)) ;; "cabal repl" sets the proper CWD
       (haskell-process-change-dir session
                                   process
                                   (haskell-session-current-dir session)))
diff --git a/haskell-session.el b/haskell-session.el
index b31f3645b..5bb117caf 100644
--- a/haskell-session.el
+++ b/haskell-session.el
@@ -36,9 +36,7 @@
 (declare-function haskell-kill-session-process "haskell-process" (&optional session))
 (declare-function haskell-process-start "haskell-process" (session))
 (declare-function haskell-process-cd "haskell-process" (&optional not-interactive))
-
-;; Dynamically scoped variables.
-(defvar haskell-process-type)
+(declare-function haskell-process-type "haskell-process" ())
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Configuration
@@ -85,11 +83,10 @@ If DONTCREATE is non-nil don't create a new session."
   ;;
   ;; Ugliness aside, if it saves us time to type it's a winner.
   ;;
-  ;; FIXME/TODO: add support for (eq 'cabal-repl haskell-process-type)
-  (require 'haskell-process) ; hack for accessing haskell-process-type
+  ;; FIXME/TODO: add support for (eq 'cabal-repl (haskell-process-type))
   (let ((modules (shell-command-to-string
                   (format "%s | %s | %s"
-                          (if (eq 'cabal-dev haskell-process-type)
+                          (if (eq 'cabal-dev (haskell-process-type))
                               (if (or (not dontcreate) (haskell-session-maybe))
                                   (format "cabal-dev -s %s/cabal-dev ghc-pkg dump"
                                           (haskell-session-cabal-dir (haskell-session)))