diff --git a/ml-proto/host/parser.mly b/ml-proto/host/parser.mly
index 9d92550205..24875067b8 100644
--- a/ml-proto/host/parser.mly
+++ b/ml-proto/host/parser.mly
@@ -233,7 +233,8 @@ expr1 :
   | LOOP labeling1 labeling1 expr_list
     { fun c -> let c' = $2 c in let c'' = $3 c' in Loop ($4 c'') }
   | BR var expr_opt { fun c -> Br ($2 c label, $3 c) }
-  | BR_IF expr var expr_opt { fun c -> Br_if ($2 c, $3 c label, $4 c) }
+  | BR_IF var expr { fun c -> Br_if ($2 c label, None, $3 c) }
+  | BR_IF var expr expr { fun c -> Br_if ($2 c label, Some ($3 c), $4 c) }
   | RETURN expr_opt
     { let at1 = ati 1 in
       fun c -> Return (label c ("return" @@ at1) @@ at1, $2 c) }
diff --git a/ml-proto/spec/ast.ml b/ml-proto/spec/ast.ml
index 086837736d..4154b859e3 100644
--- a/ml-proto/spec/ast.ml
+++ b/ml-proto/spec/ast.ml
@@ -19,7 +19,7 @@ and expr' =
   | Block of expr list
   | Loop of expr list
   | Br of var * expr option
-  | Br_if of expr * var * expr option
+  | Br_if of var * expr option * expr
   | Return of var * expr option
   | If of expr * expr
   | If_else of expr * expr * expr
diff --git a/ml-proto/spec/check.ml b/ml-proto/spec/check.ml
index fdd19b6830..42d9c4f7f1 100644
--- a/ml-proto/spec/check.ml
+++ b/ml-proto/spec/check.ml
@@ -133,6 +133,11 @@ let rec check_expr c et e =
   | Break (x, eo) ->
     check_expr_opt c (label c x) eo e.at
 
+  | Br_if (x, eo, e) ->
+    check_expr_opt c (label c x) eo e.at;
+    check_expr c (Some Int32Type) e;
+    check_type None et e.at
+
   | If (e1, e2, e3) ->
     check_expr c (Some Int32Type) e1;
     check_expr c et e2;
diff --git a/ml-proto/spec/desugar.ml b/ml-proto/spec/desugar.ml
index bad75cc63b..ebd467528e 100644
--- a/ml-proto/spec/desugar.ml
+++ b/ml-proto/spec/desugar.ml
@@ -17,6 +17,9 @@ and shift' n = function
   | Break (x, eo) ->
     let x' = if x.it < n then x else (x.it + 1) @@ x.at in
     Break (x', Lib.Option.map (shift n) eo)
+  | Br_if (x, eo, e) ->
+    let x' = if x.it < n then x else (x.it + 1) @@ x.at in
+    Br_if (x', Lib.Option.map (shift n) eo, shift n e)
   | If (e1, e2, e3) -> If (shift n e1, shift n e2, shift n e3)
   | Switch (e, xs, x, es) -> Switch (shift n e, xs, x, List.map (shift n) es)
   | Call (x, es) -> Call (x, List.map (shift n) es)
@@ -53,8 +56,7 @@ and expr' at = function
   | Ast.Block es -> Block (List.map expr es)
   | Ast.Loop es -> Block [Loop (seq es) @@ at]
   | Ast.Br (x, eo) -> Break (x, Lib.Option.map expr eo)
-  | Ast.Br_if (e, x, eo) ->
-    If (expr e, Break (x, Lib.Option.map expr eo) @@ at, opt eo)
+  | Ast.Br_if (x, eo, e) -> Br_if (x, Lib.Option.map expr eo, expr e)
   | Ast.Return (x, eo) -> Break (x, Lib.Option.map expr eo)
   | Ast.If (e1, e2) -> If (expr e1, expr e2, Nop @@ Source.after e2.at)
   | Ast.If_else (e1, e2, e3) -> If (expr e1, expr e2, expr e3)
diff --git a/ml-proto/spec/eval.ml b/ml-proto/spec/eval.ml
index 601fbf0b00..403b0859e7 100644
--- a/ml-proto/spec/eval.ml
+++ b/ml-proto/spec/eval.ml
@@ -154,6 +154,11 @@ let rec eval_expr (c : config) (e : expr) =
   | Break (x, eo) ->
     raise (label c x (eval_expr_opt c eo))
 
+  | Br_if (x, eo, e) ->
+    let v = eval_expr_opt c eo in
+    let i = int32 (eval_expr c e) e.at in
+    if i <> 0l then raise (label c x v) else None
+
   | If (e1, e2, e3) ->
     let i = int32 (eval_expr c e1) e1.at in
     eval_expr c (if i <> 0l then e2 else e3)
diff --git a/ml-proto/spec/kernel.ml b/ml-proto/spec/kernel.ml
index 36d70484d4..054ed7666e 100644
--- a/ml-proto/spec/kernel.ml
+++ b/ml-proto/spec/kernel.ml
@@ -82,6 +82,7 @@ and expr' =
   | Block of expr list                      (* execute in sequence *)
   | Loop of expr                            (* loop header *)
   | Break of var * expr option              (* break to n-th surrounding label *)
+  | Br_if of var * expr option * expr       (* conditional break *)
   | If of expr * expr * expr                (* conditional *)
   | Switch of expr * var list * var * expr list   (* table switch *)
   | Call of var * expr list                 (* call function *)
diff --git a/ml-proto/test/fac.wast b/ml-proto/test/fac.wast
index 4d19074d12..40459ca95e 100644
--- a/ml-proto/test/fac.wast
+++ b/ml-proto/test/fac.wast
@@ -62,11 +62,11 @@
     (local i64)
     (set_local 1 (i64.const 1))
     (block
-      (br_if (i64.lt_s (get_local 0) (i64.const 2)) 0)
+      (br_if 0 (i64.lt_s (get_local 0) (i64.const 2)))
       (loop
         (set_local 1 (i64.mul (get_local 1) (get_local 0)))
         (set_local 0 (i64.add (get_local 0) (i64.const -1)))
-        (br_if (i64.gt_s (get_local 0) (i64.const 1)) 0)
+        (br_if 0 (i64.gt_s (get_local 0) (i64.const 1)))
       )
     )
     (get_local 1)
diff --git a/ml-proto/test/labels.wast b/ml-proto/test/labels.wast
index 539f4ef3a3..8c51f054c6 100644
--- a/ml-proto/test/labels.wast
+++ b/ml-proto/test/labels.wast
@@ -90,23 +90,46 @@
     )
   )
 
-  (func $br_if (result i32)
+  (func $br_if0 (result i32)
     (local $i i32)
     (set_local $i (i32.const 0))
     (block $outer
       (block $inner
-        (br_if (i32.const 0) $inner)
+        (br_if $inner (i32.const 0))
         (set_local $i (i32.or (get_local $i) (i32.const 0x1)))
-        (br_if (i32.const 1) $inner)
+        (br_if $inner (i32.const 1))
         (set_local $i (i32.or (get_local $i) (i32.const 0x2)))
       )
-      (br_if (i32.const 0) $outer (set_local $i (i32.or (get_local $i) (i32.const 0x4))))
+      (br_if $outer (set_local $i (i32.or (get_local $i) (i32.const 0x4))) (i32.const 0))
       (set_local $i (i32.or (get_local $i) (i32.const 0x8)))
-      (br_if (i32.const 1) $outer (set_local $i (i32.or (get_local $i) (i32.const 0x10))))
+      (br_if $outer (set_local $i (i32.or (get_local $i) (i32.const 0x10))) (i32.const 1))
       (set_local $i (i32.or (get_local $i) (i32.const 0x20)))
     )
   )
 
+  (func $br_if1 (result i32)
+    (block $l0
+      (br_if $l0 (block $l1 (br $l1 (i32.const 1))) (i32.const 1))
+      (i32.const 1)))
+
+  (func $br_if2 (result i32)
+    (block $l0
+      (if (i32.const 1)
+        (br $l0
+          (block $l1
+            (br $l1 (i32.const 1)))))
+      (i32.const 1)))
+
+  (func $br_if3 (result i32)
+    (local $i1 i32)
+    (i32.add (block $l0
+               (br_if $l0
+                      (set_local $i1 (i32.const 1))
+                      (set_local $i1 (i32.const 2)))
+               (i32.const 0))
+             (i32.const 0))
+    (get_local $i1))
+
   (func $misc1 (result i32)
    (block $l1 (i32.xor (br $l1 (i32.const 1)) (i32.const 2)))
   )
@@ -123,7 +146,10 @@
   (export "loop5" $loop5)
   (export "switch" $switch)
   (export "return" $return)
-  (export "br_if" $br_if)
+  (export "br_if0" $br_if0)
+  (export "br_if1" $br_if1)
+  (export "br_if2" $br_if2)
+  (export "br_if3" $br_if3)
   (export "misc1" $misc1)
   (export "misc2" $misc2)
 )
@@ -143,11 +169,29 @@
 (assert_return (invoke "return" (i32.const 0)) (i32.const 0))
 (assert_return (invoke "return" (i32.const 1)) (i32.const 2))
 (assert_return (invoke "return" (i32.const 2)) (i32.const 2))
-(assert_return (invoke "br_if") (i32.const 0x1d))
+(assert_return (invoke "br_if0") (i32.const 0x1d))
+(assert_return (invoke "br_if1") (i32.const 1))
+(assert_return (invoke "br_if2") (i32.const 1))
+(assert_return (invoke "br_if3") (i32.const 2))
 (assert_return (invoke "misc1") (i32.const 1))
 (assert_return (invoke "misc2") (i32.const 1))
 
 (assert_invalid (module (func (loop $l (br $l (i32.const 0))))) "arity mismatch")
-(assert_invalid (module (func (block $l (f32.neg (br_if (i32.const 1) $l)) (nop)))) "type mismatch")
-(assert_invalid (module (func (result f32) (block $l (br_if (i32.const 1) $l (f32.const 0))))) "type mismatch")
+(assert_invalid (module (func (block $l (f32.neg (br_if $l (i32.const 1))) (nop)))) "type mismatch")
 
+(assert_invalid (module (func (result f32) (block $l (br_if $l (f32.const 0) (i32.const 1))))) "type mismatch")
+(assert_invalid (module (func (result i32) (block $l (br_if $l (f32.const 0) (i32.const 1))))) "type mismatch")
+(assert_invalid (module (func (block $l (f32.neg (br_if $l (f32.const 0) (i32.const 1)))))) "arity mismatch")
+(assert_invalid (module (func (param i32) (result i32) (block $l (f32.neg (br_if $l (f32.const 0) (get_local 0)))))) "type mismatch")
+(assert_invalid (module (func (param i32) (result f32)
+  (block $l (f32.neg (block $i (br_if $l (f32.const 3) (get_local 0)))))))
+  "type mismatch")
+(assert_invalid (module (func (block $l0 (br_if $l0 (nop) (i32.const 1)))))
+  "arity mismatch")
+(assert_invalid (module (func (result i32)
+  (block $l0
+    (if_else (i32.const 1)
+      (br $l0 (block $l1 (br $l1 (i32.const 1))))
+      (block (block $l1 (br $l1 (i32.const 1))) (nop))
+    )
+  (i32.const 1)))) "arity mismatch")