diff --git a/ml-proto/host/parser.mly b/ml-proto/host/parser.mly
index c671035a39..c4791e7fd3 100644
--- a/ml-proto/host/parser.mly
+++ b/ml-proto/host/parser.mly
@@ -329,7 +329,7 @@ module_fields :
       | Some _ -> Error.error $1.at "more than one memory section"
       | None -> {m with memory = Some $1} }
 ;
-modul :
+module_ :
   | LPAR MODULE module_fields RPAR { $3 (c0 ()) @@ at() }
 ;
 
@@ -337,8 +337,8 @@ modul :
 /* Scripts */
 
 cmd :
-  | modul { Define $1 @@ at() }
-  | LPAR ASSERTINVALID modul TEXT RPAR { AssertInvalid ($3, $4) @@ at() }
+  | module_ { Define $1 @@ at() }
+  | LPAR ASSERTINVALID module_ TEXT RPAR { AssertInvalid ($3, $4) @@ at() }
   | LPAR INVOKE TEXT expr_list RPAR
     { Invoke ($3, $4 (c0 ())) @@ at() }
   | LPAR ASSERTEQ LPAR INVOKE TEXT expr_list RPAR expr RPAR
diff --git a/ml-proto/host/print.mli b/ml-proto/host/print.mli
index 25da6cc0ce..df70541ee0 100644
--- a/ml-proto/host/print.mli
+++ b/ml-proto/host/print.mli
@@ -2,7 +2,7 @@
  * (c) 2015 Andreas Rossberg
  *)
 
-val print_module : Ast.modul -> unit
-val print_module_sig : Ast.modul -> unit
+val print_module : Ast.module_ -> unit
+val print_module_sig : Ast.module_ -> unit
 val print_value : Values.value option -> unit
 
diff --git a/ml-proto/host/script.ml b/ml-proto/host/script.ml
index 8e4e12be67..cbaab6fcbd 100644
--- a/ml-proto/host/script.ml
+++ b/ml-proto/host/script.ml
@@ -8,8 +8,8 @@ open Source
 
 type command = command' phrase
 and command' =
-  | Define of Ast.modul
-  | AssertInvalid of Ast.modul * string
+  | Define of Ast.module_
+  | AssertInvalid of Ast.module_ * string
   | Invoke of string * Ast.expr list
   | AssertEq of string * Ast.expr list * Ast.expr
   | AssertTrap of string * Ast.expr list * string
diff --git a/ml-proto/host/script.mli b/ml-proto/host/script.mli
index dd4e5ab181..3da9d0b915 100644
--- a/ml-proto/host/script.mli
+++ b/ml-proto/host/script.mli
@@ -4,8 +4,8 @@
 
 type command = command' Source.phrase
 and command' =
-  | Define of Ast.modul
-  | AssertInvalid of Ast.modul * string
+  | Define of Ast.module_
+  | AssertInvalid of Ast.module_ * string
   | Invoke of string * Ast.expr list
   | AssertEq of string * Ast.expr list * Ast.expr
   | AssertTrap of string * Ast.expr list * string
diff --git a/ml-proto/spec/ast.ml b/ml-proto/spec/ast.ml
index 1605f68b9b..f2d9b527cc 100644
--- a/ml-proto/spec/ast.ml
+++ b/ml-proto/spec/ast.ml
@@ -11,7 +11,7 @@
  *   v : value
  *   e : expr
  *   f : func
- *   m : modul
+ *   m : module_
  *
  *   t : value_type
  *   s : func_type
@@ -143,8 +143,8 @@ and import' =
 
 type table = var list Source.phrase
 
-type modul = modul' Source.phrase
-and modul' =
+type module_ = module_' Source.phrase
+and module_' =
 {
   memory : memory option;
   funcs : func list;
diff --git a/ml-proto/spec/check.ml b/ml-proto/spec/check.ml
index 1ca52be718..b33eac0d74 100644
--- a/ml-proto/spec/check.ml
+++ b/ml-proto/spec/check.ml
@@ -262,11 +262,11 @@ and check_mem_type ty sz at =
 
 (*
  * check_func : context -> func -> unit
- * check_module : context -> modul -> unit
+ * check_module : context -> module_ -> unit
  *
  * Conventions:
  *   c : context
- *   m : modul
+ *   m : module_
  *   f : func
  *   e : expr
  *   v : value
diff --git a/ml-proto/spec/check.mli b/ml-proto/spec/check.mli
index 325a0f8a11..09e2a24cb0 100644
--- a/ml-proto/spec/check.mli
+++ b/ml-proto/spec/check.mli
@@ -2,4 +2,4 @@
  * (c) 2015 Andreas Rossberg
  *)
 
-val check_module : Ast.modul -> unit (* raise Error *)
+val check_module : Ast.module_ -> unit (* raise Error *)
diff --git a/ml-proto/spec/eval.ml b/ml-proto/spec/eval.ml
index 16eab27afa..15aec80f17 100644
--- a/ml-proto/spec/eval.ml
+++ b/ml-proto/spec/eval.ml
@@ -36,22 +36,22 @@ type label = value option -> exn
 
 type config =
 {
-  modul : instance;
+  module_ : instance;
   locals : value ref list;
   labels : label list;
   return : label
 }
 
 let page_size c =
-  I32.of_int32 (Int32.of_int c.modul.host.page_size)
+  I32.of_int32 (Int32.of_int c.module_.host.page_size)
 
 let lookup category list x =
   try List.nth list x.it with Failure _ ->
     error x.at ("runtime: undefined " ^ category ^ " " ^ string_of_int x.it)
 
-let func c x = lookup "function" c.modul.funcs x
-let import c x = lookup "import" c.modul.imports x
-let table c x y = lookup "entry" (lookup "table" c.modul.tables x) y
+let func c x = lookup "function" c.module_.funcs x
+let import c x = lookup "import" c.module_.imports x
+let table c x y = lookup "entry" (lookup "table" c.module_.tables x) y
 let local c x = lookup "local" c.locals x
 let label c x = lookup "label" c.labels x
 
@@ -145,7 +145,7 @@ let rec eval_expr (c : config) (e : expr) =
 
   | Call (x, es) ->
     let vs = List.map (fun vo -> some (eval_expr c vo) vo.at) es in
-    eval_func c.modul (func c x) vs
+    eval_func c.module_ (func c x) vs
 
   | CallImport (x, es) ->
     let vs = List.map (fun ev -> some (eval_expr c ev) ev.at) es in
@@ -155,7 +155,7 @@ let rec eval_expr (c : config) (e : expr) =
     let i = int32 (eval_expr c e1) e1.at in
     let vs = List.map (fun vo -> some (eval_expr c vo) vo.at) es in
     (* TODO: The conversion to int could overflow. *)
-    eval_func c.modul (table c x (Int32.to_int i @@ e1.at)) vs
+    eval_func c.module_ (table c x (Int32.to_int i @@ e1.at)) vs
 
   | Return eo ->
     raise (c.return (eval_expr_option c eo))
@@ -171,28 +171,28 @@ let rec eval_expr (c : config) (e : expr) =
   | Load ({ty; align = _}, e1) ->
     let v1 = some (eval_expr c e1) e1.at in
     let a = Memory.address_of_value v1 in
-    (try Some (Memory.load c.modul.memory a ty)
+    (try Some (Memory.load c.module_.memory a ty)
     with exn -> memory_error e.at exn)
 
   | Store ({ty = _; align = _}, e1, e2) ->
     let v1 = some (eval_expr c e1) e1.at in
     let v2 = some (eval_expr c e2) e2.at in
     let a = Memory.address_of_value v1 in
-    (try Memory.store c.modul.memory a v2
+    (try Memory.store c.module_.memory a v2
     with exn -> memory_error e.at exn);
     None
 
   | LoadExtend ({memop = {ty; align = _}; sz; ext}, e1) ->
     let v1 = some (eval_expr c e1) e1.at in
     let a = Memory.address_of_value v1 in
-    (try Some (Memory.load_extend c.modul.memory a sz ext ty)
+    (try Some (Memory.load_extend c.module_.memory a sz ext ty)
     with exn -> memory_error e.at exn)
 
   | StoreTrunc ({memop = {ty; align = _}; sz}, e1, e2) ->
     let v1 = some (eval_expr c e1) e1.at in
     let v2 = some (eval_expr c e2) e2.at in
     let a = Memory.address_of_value v1 in
-    (try Memory.store_trunc c.modul.memory a sz v2
+    (try Memory.store_trunc c.module_.memory a sz v2
     with exn -> memory_error e.at exn);
     None
 
@@ -235,14 +235,14 @@ let rec eval_expr (c : config) (e : expr) =
     Some (Int32 (page_size c))
 
   | MemorySize ->
-    Some (Int32 (I32.of_int32 (Int32.of_int (Memory.size c.modul.memory))))
+    Some (Int32 (I32.of_int32 (Int32.of_int (Memory.size c.module_.memory))))
 
   | ResizeMemory e ->
     let i = int32 (eval_expr c e) e.at in
     if (I32.rem_u i (page_size c)) <> I32.zero then
       error e.at "runtime: resize_memory operand not multiple of page_size";
     (* TODO: The conversion to int could overflow. *)
-    Memory.resize c.modul.memory (Int32.to_int i);
+    Memory.resize c.module_.memory (Int32.to_int i);
     None
 
 and eval_expr_option c eo =
@@ -265,7 +265,7 @@ and eval_func (m : instance) (f : func) (evs : value list) =
   let args = List.map ref evs in
   let vars = List.map (fun t -> ref (default_value t.it)) f.it.locals in
   let locals = args @ vars in
-  let c = {modul = m; locals; labels = []; return = Return.label} in
+  let c = {module_ = m; locals; labels = []; return = Return.label} in
   try eval_expr c f.it.body
   with Return.Label vo -> vo
 
diff --git a/ml-proto/spec/eval.mli b/ml-proto/spec/eval.mli
index f6f6c70fa4..4c737a0103 100644
--- a/ml-proto/spec/eval.mli
+++ b/ml-proto/spec/eval.mli
@@ -7,7 +7,7 @@ type value = Values.value
 type import = value list -> value option
 type host_params = {page_size : Memory.size}
 
-val init : Ast.modul -> import list -> host_params -> instance
+val init : Ast.module_ -> import list -> host_params -> instance
 val invoke : instance -> string -> value list -> value option
   (* raise Error.Error *)
 val eval : Ast.expr -> value option (* raise Error.Error *)