diff --git a/CHANGES.md b/CHANGES.md
index 19dd01fbdbe..558ffb360a9 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -91,6 +91,8 @@ next
 - Make `(diff a b)` ignore trailing cr on Windows and add `(cmp a b)` for
   comparing binary files (#904, fix #844, @diml)
 
+- Make `dev` the default build profile (#920, @diml)
+
 1.0+beta20 (10/04/2018)
 -----------------------
 
diff --git a/Makefile b/Makefile
index 722497e54c1..0c65c2519e7 100644
--- a/Makefile
+++ b/Makefile
@@ -4,10 +4,10 @@ BIN := ./_build/default/bin/main_dune.exe
 -include Makefile.dev
 
 default: boot.exe
-	./boot.exe --dev
+	./boot.exe
 
 release: boot.exe
-	./boot.exe
+	./boot.exe --release
 
 boot.exe: bootstrap.ml
 	ocaml bootstrap.ml
@@ -21,13 +21,13 @@ uninstall:
 reinstall: uninstall reinstall
 
 test:
-	$(BIN) runtest --dev
+	$(BIN) runtest
 
 test-js:
-	$(BIN) build @runtest-js --dev
+	$(BIN) build @runtest-js
 
 test-all:
-	$(BIN) build @runtest @runtest-js --dev
+	$(BIN) build @runtest @runtest-js
 
 promote:
 	$(BIN) promote
@@ -35,7 +35,7 @@ promote:
 accept-corrections: promote
 
 all-supported-ocaml-versions:
-	$(BIN) build --dev @install @runtest --workspace dune-workspace.dev --root .
+	$(BIN) build @install @runtest --workspace dune-workspace.dev --root .
 
 clean:
 	$(BIN) clean
@@ -52,7 +52,7 @@ livedoc:
 	  -p 8888 -q  --host $(shell hostname) -r '\.#.*'
 
 update-jbuilds: $(BIN)
-	$(BIN) build --dev @doc/runtest --auto-promote
+	$(BIN) build @doc/runtest --auto-promote
 
 .PHONY: default install uninstall reinstall clean test doc
 .PHONY: promote accept-corrections opam-release
diff --git a/appveyor.yml b/appveyor.yml
index a426458418a..71016ad4d6c 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -7,7 +7,7 @@ install:
 build_script:
   - cd "%APPVEYOR_BUILD_FOLDER%"
   - ocaml bootstrap.ml
-  - boot.exe --dev
+  - boot.exe
   - copy _build\install\default\bin\dune.exe dune.exe
   - dune.exe build @test\blackbox-tests\windows-diff
 
diff --git a/bin/main.ml b/bin/main.ml
index 6ffdfdd953e..7e5d872bba4 100644
--- a/bin/main.ml
+++ b/bin/main.ml
@@ -347,12 +347,26 @@ let common =
          & info ["dev"] ~docs
              ~doc:{|Same as $(b,--profile dev)|})
   in
+  let dev =
+    match Which_program.t with
+    | Jbuilder -> dev
+    | Dune ->
+      let check = function
+        | false -> `Ok false
+        | true ->
+          `Error (true, "--dev is no longer accepted as it is now the default.")
+      in
+      Term.(ret (const check $ dev))
+  in
   let profile =
     Arg.(value
          & opt (some string) None
          & info ["profile"] ~docs
-             ~doc:{|Select the build profile, for instance $(b,dev) or $(b,release).
-                    The default is $(b,default).|})
+             ~doc:
+               (sprintf
+                  {|Select the build profile, for instance $(b,dev) or
+                    $(b,release). The default is $(b,%s).|}
+                  Config.default_build_profile))
   in
   let profile =
     let merge dev profile =
@@ -567,7 +581,7 @@ let installed_libraries =
     Scheduler.go ~log:(Log.create common) ~common
       (Context.create
          (Default { targets = [Native]
-                  ; profile = "default" })
+                  ; profile = Config.default_build_profile })
          ~env
        >>= fun ctxs ->
        let ctx = List.hd ctxs in
diff --git a/doc/jbuild.rst b/doc/jbuild.rst
index 9009f45757b..369c69eefd9 100644
--- a/doc/jbuild.rst
+++ b/doc/jbuild.rst
@@ -1159,8 +1159,9 @@ using ``(js_of_ocaml (<js_of_ocaml-options>))``.
 
 ``<flags>`` is specified in the `Ordered set language`_.
 
-The default value for ``(flags ...)`` depends on whether ``--dev`` is passed to
-Jbuilder. ``--dev`` will enable sourcemap and the pretty JavaScript output.
+The default value for ``(flags ...)`` depends on the selected build
+profile. The build profile ``dev`` (the default) will enable sourcemap
+and the pretty JavaScript output.
 
 .. _user-actions:
 
diff --git a/doc/terminology.rst b/doc/terminology.rst
index 5339c962408..0afb5801959 100644
--- a/doc/terminology.rst
+++ b/doc/terminology.rst
@@ -64,9 +64,9 @@ Terminology
 
 - **build profile**: a global setting that influence various
   defaults. It can be set from the command line using ``--profile
-  <profile>`` or from ``jbuild-workspace`` files. The following
+  <profile>`` or from ``dune-workspace`` files. The following
   profiles are standard:
 
-  -  ``default`` which is the default profile when none is set explicitely
   -  ``release`` which is the profile used for opam releases
-  -  ``dev`` which has stricter warnings
+  -  ``dev`` which is the default profile when none is set explicitely, it
+     has stricter warnings that the ``release`` one
diff --git a/doc/usage.rst b/doc/usage.rst
index f62605a6362..4a5a9a9e1f9 100644
--- a/doc/usage.rst
+++ b/doc/usage.rst
@@ -224,7 +224,7 @@ follows:
 
 ::
 
-    build: [["jbuilder" "build" "-p" name "-j" jobs]]
+    build: [["dune" "build" "-p" name "-j" jobs]]
 
 ``-p pkg`` is a shorthand for ``--root . --only-packages pkg --profile
 release``. ``-p`` is the short version of
@@ -364,7 +364,7 @@ write a ``(profile ...)`` stanza. For instance:
 
 .. code:: scheme
 
-    (profile dev)
+    (profile release)
 
 Note that the command line option ``--profile`` has precedence over
 this stanza.
@@ -436,8 +436,9 @@ It supports two modes of compilation:
   separately and then linked together. This mode is useful during development as
   it builds more quickly.
 
-The separate compilation mode will be selected when passing ``--dev`` to
-jbuilder. There is currently no other way to control this behaviour.
+The separate compilation mode will be selected when the build profile
+is ``dev``, which is the default. There is currently no other way to
+control this behaviour.
 
 See the section about :ref:`jbuild-jsoo` for passing custom flags to the
 js_of_ocaml compiler
diff --git a/dune.opam b/dune.opam
index f87556a7719..6dad0a7828a 100644
--- a/dune.opam
+++ b/dune.opam
@@ -8,8 +8,8 @@ license: "MIT"
 build: [
   ["ocaml" "configure.ml" "--libdir" lib]
   ["ocaml" "bootstrap.ml"]
-  ["./boot.exe" "--subst"] {pinned}
-  ["./boot.exe" "-j" jobs]
+  ["./boot.exe" "--release" "--subst"] {pinned}
+  ["./boot.exe" "--release" "-j" jobs]
 ]
 available: [ ocaml-version >= "4.02.3" ]
 conflicts: [
diff --git a/src/config.ml b/src/config.ml
index ea381510ecb..28d4d45eca6 100644
--- a/src/config.ml
+++ b/src/config.ml
@@ -24,6 +24,11 @@ let jbuilder_keep_fname = ".jbuilder-keep"
 let inside_emacs = Option.is_some (Env.get Env.initial "INSIDE_EMACS")
 let inside_dune  = Option.is_some (Env.get Env.initial "INSIDE_DUNE")
 
+let default_build_profile =
+  match Which_program.t with
+  | Dune     -> "dev"
+  | Jbuilder -> "release"
+
 open Sexp.Of_sexp
 
 module Display = struct
diff --git a/src/config.mli b/src/config.mli
index e82b847aae5..7e03b92e78d 100644
--- a/src/config.mli
+++ b/src/config.mli
@@ -21,6 +21,8 @@ val inside_emacs : bool
 (** Are we running insinde Dune? *)
 val inside_dune : bool
 
+val default_build_profile : string
+
 (** Jbuilder configuration *)
 
 module Display : sig
diff --git a/src/dune b/src/dune
index 254d8cf3658..0baaf2a05d8 100644
--- a/src/dune
+++ b/src/dune
@@ -7,7 +7,8 @@
               re
               opam_file_format
               usexp
-              ocaml_config)
+              ocaml_config
+              which_program)
  (synopsis    "Internal Dune library, do not use!"))
 
 (ocamllex meta_lexer glob_lexer dune_lexer)
diff --git a/src/main.ml b/src/main.ml
index 33c1f649ac5..22c8754fd85 100644
--- a/src/main.ml
+++ b/src/main.ml
@@ -77,7 +77,9 @@ let setup ?(log=Log.no_log)
                               | None   -> Native
                               | Some x -> Named x
                             ]
-                          ; profile = Option.value profile ~default:"default"
+                          ; profile =
+                              Option.value profile
+                                ~default:Config.default_build_profile
                           }]
           }
   in
@@ -229,8 +231,8 @@ let bootstrap () =
     let profile = ref None in
     Arg.parse
       [ "-j"           , String concurrency_arg, "JOBS concurrency"
-      ; "--dev"        , Unit (fun () -> profile := Some "dev"),
-        " set development mode"
+      ; "--release"        , Unit (fun () -> profile := Some "release"),
+        " set release mode"
       ; "--display"    , display_mode          , " set the display mode"
       ; "--subst"      , Unit subst            ,
         " substitute watermarks in source files"
@@ -242,7 +244,7 @@ let bootstrap () =
     Clflags.debug_dep_path := true;
     let config =
       (* Only load the configuration with --dev *)
-      if !profile = Some "dev" then
+      if !profile <> Some "release" then
         Config.load_user_config_file ()
       else
         Config.default
diff --git a/src/workspace.ml b/src/workspace.ml
index 1ac468c6b1d..cc177cf8f22 100644
--- a/src/workspace.ml
+++ b/src/workspace.ml
@@ -120,7 +120,7 @@ let t ?x ?profile:cmdline_profile sexps =
     | _ :: (loc, _) :: _, _ ->
       Loc.fail loc "profile defined too many times"
     | _, Some p -> p
-    | [], None -> "default"
+    | [], None -> Config.default_build_profile
     | [(_, p)], None -> p
   in
   let { merlin_context; contexts } =
diff --git a/test/blackbox-tests/test-cases/env/run.t b/test/blackbox-tests/test-cases/env/run.t
index 3f9588ed6d3..77562762a24 100644
--- a/test/blackbox-tests/test-cases/env/run.t
+++ b/test/blackbox-tests/test-cases/env/run.t
@@ -1,34 +1,34 @@
-  $ dune printenv .
+  $ dune printenv --profile default .
   (
    (flags (-w -40 -plop))
    (ocamlc_flags (-g))
    (ocamlopt_flags (-g))
   )
-  $ dune printenv src
+  $ dune printenv --profile default src
   (
    (flags (-w -40 -plop -truc))
    (ocamlc_flags (-g))
    (ocamlopt_flags (-g))
   )
-  $ dune printenv bin
+  $ dune printenv --profile default bin
   (
    (flags (-machin))
    (ocamlc_flags (-g))
    (ocamlopt_flags (-g))
   )
-  $ dune printenv vendor
+  $ dune printenv --profile default vendor
   (
    (flags (-w -40 -plop))
    (ocamlc_flags (-g))
    (ocamlopt_flags (-g))
   )
-  $ dune printenv vendor/a
+  $ dune printenv --profile default vendor/a
   (
    (flags (-w -40 -bidule))
    (ocamlc_flags (-g))
    (ocamlopt_flags (-g))
   )
-  $ dune printenv vendor/a/src
+  $ dune printenv --profile default vendor/a/src
   (
    (flags (-w -40 -bidule -pouet))
    (ocamlc_flags (-g))
diff --git a/test/blackbox-tests/test-cases/exec-cmd/run.t b/test/blackbox-tests/test-cases/exec-cmd/run.t
index e11282b8b4b..8942780ce1b 100644
--- a/test/blackbox-tests/test-cases/exec-cmd/run.t
+++ b/test/blackbox-tests/test-cases/exec-cmd/run.t
@@ -8,7 +8,7 @@
       ocamlopt .foo.eobjs/foo.{cmx,o}
       ocamlopt foo.exe
   Foo
-  $ dune exec --dev ./foo.exe --display short
+  $ dune exec --profile release ./foo.exe --display short
         ocamlc .foo.eobjs/foo.{cmi,cmo,cmt}
       ocamlopt .foo.eobjs/foo.{cmx,o}
       ocamlopt foo.exe
diff --git a/test/blackbox-tests/test-cases/github660/explicit-interfaces/lib_sub.ml b/test/blackbox-tests/test-cases/github660/explicit-interfaces/lib_sub.ml
deleted file mode 100644
index e33bd25c296..00000000000
--- a/test/blackbox-tests/test-cases/github660/explicit-interfaces/lib_sub.ml
+++ /dev/null
@@ -1 +0,0 @@
-let hello = "hello"
diff --git a/test/blackbox-tests/test-cases/github660/no-interfaces/lib_sub.ml b/test/blackbox-tests/test-cases/github660/no-interfaces/lib_sub.ml
deleted file mode 100644
index e33bd25c296..00000000000
--- a/test/blackbox-tests/test-cases/github660/no-interfaces/lib_sub.ml
+++ /dev/null
@@ -1 +0,0 @@
-let hello = "hello"
diff --git a/test/blackbox-tests/test-cases/github660/run.t b/test/blackbox-tests/test-cases/github660/run.t
index 9eff5181bd6..ef75ae81bb1 100644
--- a/test/blackbox-tests/test-cases/github660/run.t
+++ b/test/blackbox-tests/test-cases/github660/run.t
@@ -1,10 +1,13 @@
+  $ echo 'let hello = "hello"' > explicit-interfaces/lib_sub.ml
+  $ echo 'let hello = "hello"' > no-interfaces/lib_sub.ml
+
 When there are explicit interfaces, modules must be rebuilt.
 
   $ dune runtest --root explicit-interfaces
   Entering directory 'explicit-interfaces'
           main alias runtest
   hello
-  $ echo 'let x = 1' >> explicit-interfaces/lib_sub.ml
+  $ echo 'let _x = 1' >> explicit-interfaces/lib_sub.ml
   $ dune runtest --root explicit-interfaces
   Entering directory 'explicit-interfaces'
           main alias runtest
@@ -17,7 +20,7 @@ to rely on these.
   Entering directory 'no-interfaces'
           main alias runtest
   hello
-  $ echo 'let x = 1' >> no-interfaces/lib_sub.ml
+  $ echo 'let _x = 1' >> no-interfaces/lib_sub.ml
   $ dune runtest --root no-interfaces
   Entering directory 'no-interfaces'
           main alias runtest
diff --git a/test/blackbox-tests/test-cases/js_of_ocaml/run.t b/test/blackbox-tests/test-cases/js_of_ocaml/run.t
index adfb925f7e2..f046a83e7da 100644
--- a/test/blackbox-tests/test-cases/js_of_ocaml/run.t
+++ b/test/blackbox-tests/test-cases/js_of_ocaml/run.t
@@ -1,4 +1,4 @@
-  $ dune build --display short --dev bin/technologic.bc.js @install lib/x.cma.js lib/x__Y.cmo.js bin/z.cmo.js
+  $ dune build --display short bin/technologic.bc.js @install lib/x.cma.js lib/x__Y.cmo.js bin/z.cmo.js
         ocamlc lib/stubs$ext_obj
     ocamlmklib lib/dllx_stubs$ext_dll,lib/libx_stubs$ext_lib
       ocamlopt .ppx/js_of_ocaml-ppx/ppx.exe
@@ -34,7 +34,7 @@
   use it
   break it
   fix it
-  $ dune build --display short bin/technologic.bc.js @install
+  $ dune build --display short bin/technologic.bc.js @install --profile release
         ocamlc lib/.x.objs/x__.{cmi,cmo,cmt}
         ocamlc lib/.x.objs/x__Y.{cmi,cmo,cmt}
         ocamlc lib/.x.objs/x.{cmi,cmo,cmt}
diff --git a/test/blackbox-tests/test-cases/merlin-tests/run.t b/test/blackbox-tests/test-cases/merlin-tests/run.t
index 53ee57d9d39..91b53db185d 100644
--- a/test/blackbox-tests/test-cases/merlin-tests/run.t
+++ b/test/blackbox-tests/test-cases/merlin-tests/run.t
@@ -1,4 +1,4 @@
-  $ dune build @print-merlins --display short
+  $ dune build @print-merlins --display short --profile release
       ocamldep sanitize-dot-merlin/.sanitize_dot_merlin.eobjs/sanitize_dot_merlin.ml.d
         ocamlc sanitize-dot-merlin/.sanitize_dot_merlin.eobjs/sanitize_dot_merlin.{cmi,cmo,cmt}
       ocamlopt sanitize-dot-merlin/.sanitize_dot_merlin.eobjs/sanitize_dot_merlin.{cmx,o}
diff --git a/test/blackbox-tests/test-cases/ocamldep-multi-stanzas/run.t b/test/blackbox-tests/test-cases/ocamldep-multi-stanzas/run.t
index 617a8322e50..8513f582eb4 100644
--- a/test/blackbox-tests/test-cases/ocamldep-multi-stanzas/run.t
+++ b/test/blackbox-tests/test-cases/ocamldep-multi-stanzas/run.t
@@ -1,4 +1,4 @@
-  $ dune exec ./test.exe --debug-dep --display short --root jbuild
+  $ dune exec ./test.exe --debug-dep --display short --root jbuild --profile release
   Entering directory 'jbuild'
   File "jbuild", line 1, characters 0-0:
   Warning: Module "Lib" is used in several stanzas:
diff --git a/test/blackbox-tests/test-cases/ppx-rewriter/ppx/fooppx.ml b/test/blackbox-tests/test-cases/ppx-rewriter/ppx/fooppx.ml
index d66308a9708..ceca278aeb1 100644
--- a/test/blackbox-tests/test-cases/ppx-rewriter/ppx/fooppx.ml
+++ b/test/blackbox-tests/test-cases/ppx-rewriter/ppx/fooppx.ml
@@ -8,7 +8,7 @@ let () =
            ; "-arg", Arg.Set_string arg, ""
            ])
     Migrate_parsetree.Versions.ocaml_405
-    (fun _ cookies ->
+    (fun _ _cookies ->
        if not !flag then (
          Format.eprintf "pass -flag to fooppx@.%!";
          exit 1
diff --git a/test/blackbox-tests/test-cases/use-meta/foobarlib/foobarlib.ml b/test/blackbox-tests/test-cases/use-meta/foobarlib/foobarlib.ml
index a691c05551a..5bde92ff950 100644
--- a/test/blackbox-tests/test-cases/use-meta/foobarlib/foobarlib.ml
+++ b/test/blackbox-tests/test-cases/use-meta/foobarlib/foobarlib.ml
@@ -1,4 +1,4 @@
-open Str
+open! Str
 
 let foo () =
   print_endline "foobarlib"
diff --git a/test/bulk-update.sh b/test/bulk-update.sh
index 5a526dfd005..da4add3cf8d 100644
--- a/test/bulk-update.sh
+++ b/test/bulk-update.sh
@@ -6,15 +6,15 @@
 # the current test succeeds. It uses inotifywait to detect changes to
 # the test.
 
-DUNE=_build/default/bin/main.exe
+DUNE=_build/default/bin/main_dune.exe
 
 LIST=$(mktemp)
 trap "rm -f $LIST" EXIT
 
 echo "Computing the list of failing tests..."
 $DUNE runtest test/blackbox-tests \
-      --diff-command "echo >> $LIST" --dev &> /dev/null
-TESTS=$(cat /tmp/list |cut -d/ -f4 |sed 's/^//')
+      --diff-command "echo >> $LIST" &> /dev/null
+TESTS=$(cat $LIST |cut -d/ -f4 |sed 's/^//')
 rm -f $LIST
 
 count=0
@@ -32,7 +32,7 @@ for t in $TESTS; do
         echo "$title"
         echo "${title//?/=}"
         echo
-        $DUNE build --dev @test/blackbox-tests/$t && break
+        $DUNE build @test/blackbox-tests/$t && break
         inotifywait $(find test/blackbox-tests/test-cases/$t -type d) \
                     -e modify,attrib,close_write,move,create,delete
     done
diff --git a/test/unit-tests/dune b/test/unit-tests/dune
index 42e50646215..b5355c99546 100644
--- a/test/unit-tests/dune
+++ b/test/unit-tests/dune
@@ -3,7 +3,7 @@
  (modules expect_test)
  (link_flags (-linkall))
  (modes byte)
- (libraries unix dune compiler-libs.toplevel test_common))
+ (libraries which_program_dune unix dune compiler-libs.toplevel test_common))
 
 (ocamllex expect_test)