diff --git a/sledge/Makefile b/sledge/Makefile
index 378481fce..6dd59783e 100644
--- a/sledge/Makefile
+++ b/sledge/Makefile
@@ -8,10 +8,11 @@ default: exes
 
 EXES = src/sledge
 INSTALLS = sledge
-FMTS = @_build/dev/src/fmt
+FMTS = @_build/dbg/src/fmt
 
-DBG_TARGETS = $(patsubst %,_build/dev/%.exe,$(EXES)) $(patsubst %,_build/dev/%.install,$(INSTALLS)) _build/dev/sledge-help.txt
-OPT_TARGETS = $(patsubst %,_build/release/%.exe,$(EXES)) $(patsubst %,_build/release/%.install,$(INSTALLS)) _build/release/sledge-help.txt
+DBG_TARGETS = $(patsubst %,_build/dbg/%.exe,$(EXES)) $(patsubst %,_build/dbg/%.install,$(INSTALLS)) _build/dbg/sledge-help.txt
+OPT_TARGETS = $(patsubst %,_build/opt/%.exe,$(EXES)) $(patsubst %,_build/opt/%.install,$(INSTALLS)) _build/opt/sledge-help.txt
+DBG_OPT_TARGETS = $(patsubst %,_build/dbg-opt/%.exe,$(EXES)) $(patsubst %,_build/dbg-opt/%.install,$(INSTALLS)) _build/dbg-opt/sledge-help.txt
 
 DUNEINS = $(shell find src model -name dune.in)
 DUNES = $(patsubst %.in,%,$(DUNEINS))
@@ -31,27 +32,31 @@ check: setup
 
 .PHONY: exes
 exes: setup
-	dune build $(DBG_TARGETS) $(OPT_TARGETS)
+	dune build $(DBG_TARGETS) $(DBG_OPT_TARGETS) $(OPT_TARGETS)
 
 .PHONY: dbg
 dbg: setup
 	dune build $(DBG_TARGETS)
 
+.PHONY: do
+do: setup
+	dune build $(DBG_OPT_TARGETS)
+
 .PHONY: opt
 opt: setup
 	dune build $(OPT_TARGETS)
 
 .PHONY: watch
 watch: setup
-	dune build --watch $(DBG_TARGETS) $(OPT_TARGETS)
+	dune build --watch $(DBG_TARGETS) $(DBG_OPT_TARGETS) $(OPT_TARGETS)
 
 .PHONY: test
 test: setup
-	dune build @_build/dev/runtest --auto-promote
+	dune build @_build/dbg/runtest --auto-promote
 
 .PHONY: ci-test
 ci-test: setup
-	dune build @_build/dev/runtest
+	dune build @_build/dbg/runtest
 
 BISECT_DIR = $(CURDIR)/_coverage/out
 
diff --git a/sledge/bin/sledge b/sledge/bin/sledge
index 9c49f9623..09fa49bec 120000
--- a/sledge/bin/sledge
+++ b/sledge/bin/sledge
@@ -1 +1 @@
-../_build/install/release/bin/sledge
\ No newline at end of file
+../_build/install/opt/bin/sledge
\ No newline at end of file
diff --git a/sledge/bin/sledge.dbg b/sledge/bin/sledge.dbg
index f2558589e..b2907c46b 120000
--- a/sledge/bin/sledge.dbg
+++ b/sledge/bin/sledge.dbg
@@ -1 +1 @@
-../_build/install/dev/bin/sledge
\ No newline at end of file
+../_build/install/dbg/bin/sledge
\ No newline at end of file
diff --git a/sledge/dune-common.in b/sledge/dune-common.in
index 5b6148656..2720e9776 100644
--- a/sledge/dune-common.in
+++ b/sledge/dune-common.in
@@ -14,19 +14,21 @@ let common_flags =
 
 let ocamlc_flags =
   match Jbuild_plugin.V1.context with
-  | "release" -> "-w -26-32 -noassert"
+  | "opt" | "dbg-opt" -> "-w -26-32 -noassert"
   | _ -> "-g"
 
 let ocamlopt_flags =
   match Jbuild_plugin.V1.context with
-  | "release" -> ocamlc_flags ^ " -w -a -O3"
+  | "opt" | "dbg-opt" -> ocamlc_flags ^ " -w -a -O3"
   | _ -> ocamlc_flags
 
 let coverage_ppx =
   match Jbuild_plugin.V1.context with "coverage" -> "bisect_ppx" | _ -> ""
 
 let ppx_flags =
-  match Jbuild_plugin.V1.context with "dev" -> "--debug" | _ -> ""
+  match Jbuild_plugin.V1.context with
+  | "dbg" | "dbg-opt" -> "--debug"
+  | _ -> ""
 
 let flags exe_or_lib deps =
   Printf.sprintf
diff --git a/sledge/dune-workspace b/sledge/dune-workspace
index abe850e5d..bfc0b75fd 100644
--- a/sledge/dune-workspace
+++ b/sledge/dune-workspace
@@ -1,5 +1,6 @@
 (lang dune 1.0)
 
-(context (opam (switch sledge) (name dev) (merlin)))
+(context (opam (switch sledge) (name dbg) (merlin)))
+(context (opam (switch sledge) (name dbg-opt)))
+(context (opam (switch sledge) (name opt)))
 (context (opam (switch sledge) (name coverage)))
-(context (opam (switch sledge) (name release)))
diff --git a/sledge/sledge.opam b/sledge/sledge.opam
index c9ebcad46..fe17804ab 100644
--- a/sledge/sledge.opam
+++ b/sledge/sledge.opam
@@ -7,7 +7,7 @@ dev-repo: "git://github.com/facebook/infer.git"
 license: "MIT"
 build: [
   [make "setup"]
-  ["dune" "build" "-p" name "-j" jobs]
+  ["dune" "build" "-p" name "--profile" "opt" "-j" jobs]
 ]
 depends: [
   "ocaml"
diff --git a/sledge/src/import/import.ml b/sledge/src/import/import.ml
index 0363b5ae1..32467f953 100644
--- a/sledge/src/import/import.ml
+++ b/sledge/src/import/import.ml
@@ -108,18 +108,20 @@ module Invariant = struct
   include Base.Invariant
 
   let invariant here t sexp_of_t f =
-    try f ()
-    with exn ->
-      let bt = Caml.Printexc.get_raw_backtrace () in
-      let exn =
-        Error.to_exn
-          (Error.create_s
-             (Base.Sexp.message "invariant failed"
-                [ ("", Source_code_position.sexp_of_t here)
-                ; ("exn", sexp_of_exn exn)
-                ; ("", sexp_of_t t) ]))
-      in
-      Caml.Printexc.raise_with_backtrace exn bt
+    assert (
+      ( try f ()
+        with exn ->
+          let bt = Caml.Printexc.get_raw_backtrace () in
+          let exn =
+            Error.to_exn
+              (Error.create_s
+                 (Base.Sexp.message "invariant failed"
+                    [ ("", Source_code_position.sexp_of_t here)
+                    ; ("exn", sexp_of_exn exn)
+                    ; ("", sexp_of_t t) ]))
+          in
+          Caml.Printexc.raise_with_backtrace exn bt ) ;
+      true )
 end
 
 let map_preserving_phys_equal map t ~f =