3 files changed, 21 insertions, 17 deletions
diff --git a/src/passes/RemoveUnusedBrs.cpp b/src/passes/RemoveUnusedBrs.cpp
index 263cea655..59d3af6fc 100644
--- a/src/passes/RemoveUnusedBrs.cpp
+++ b/src/passes/RemoveUnusedBrs.cpp
@@ -189,7 +189,7 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs, Visitor<R
     // finally, we may have simplified ifs enough to turn them into selects
     struct Selectifier : public WalkerPass<PostWalker<Selectifier, Visitor<Selectifier>>> {
       void visitIf(If* curr) {
-        if (curr->ifFalse) {
+        if (curr->ifFalse && isConcreteWasmType(curr->ifTrue->type) && isConcreteWasmType(curr->ifFalse->type)) {
           // if with else, consider turning it into a select if there is no control flow
           // TODO: estimate cost
           EffectAnalyzer condition(curr->condition);
diff --git a/src/wasm-validator.h b/src/wasm-validator.h
index 5844dafcd..8e989c94d 100644
--- a/src/wasm-validator.h
+++ b/src/wasm-validator.h
@@ -280,6 +280,10 @@ public:
       default: abort();
     }
   }
+  void visitSelect(Select* curr) {
+    shouldBeUnequal(curr->ifTrue->type, none, curr, "select left must be valid");
+    shouldBeUnequal(curr->ifFalse->type, none, curr, "select right must be valid");
+  }
 
   void visitReturn(Return* curr) {
     if (curr->value) {
diff --git a/test/passes/remove-unused-brs.txt b/test/passes/remove-unused-brs.txt
index de6dc4779..1c5c8e713 100644
--- a/test/passes/remove-unused-brs.txt
+++ b/test/passes/remove-unused-brs.txt
@@ -117,7 +117,8 @@
   )
   (func $b12-yes (type $1)
     (block $topmost
-      (select
+      (if
+        (i32.const 1)
         (block $block1
           (drop
             (i32.const 12)
@@ -138,7 +139,6 @@
             )
           )
         )
-        (i32.const 1)
       )
     )
   )
@@ -221,42 +221,42 @@
   )
   (func $b17 (type $1)
     (block $a
-      (select
+      (if
+        (i32.const 0)
         (block $block1
         )
         (block $block3
         )
-        (i32.const 0)
       )
     )
     (block $a
-      (select
+      (if
+        (i32.const 0)
         (drop
           (i32.const 1)
         )
         (block $block6
         )
-        (i32.const 0)
       )
     )
     (block $a
-      (select
+      (if
+        (i32.const 0)
         (block $block8
         )
         (drop
           (i32.const 1)
         )
-        (i32.const 0)
       )
     )
     (block $c
       (block $b
-        (select
+        (if
+          (i32.const 0)
           (block $block11
           )
           (block $block13
           )
-          (i32.const 0)
         )
       )
     )
@@ -272,11 +272,11 @@
   )
   (func $ret-3 (type $1)
     (block $block0
-      (select
+      (if
+        (i32.const 0)
         (nop)
         (block $block3
         )
-        (i32.const 0)
       )
     )
   )
@@ -340,7 +340,10 @@
           (i32.const 1)
         )
       )
-      (select
+      (if
+        (block $a
+          (i32.const 0)
+        )
         (block $a
           (block $block11
             (drop
@@ -355,9 +358,6 @@
             )
           )
         )
-        (block $a
-          (i32.const 0)
-        )
       )
     )
   )