diff --git a/runtime/vm/compiler/backend/compile_type.h b/runtime/vm/compiler/backend/compile_type.h
index 217ab1ebdbb..ded5fa606f4 100644
--- a/runtime/vm/compiler/backend/compile_type.h
+++ b/runtime/vm/compiler/backend/compile_type.h
@@ -80,7 +80,13 @@ class CompileType : public ZoneAllocated {
   // abstract type. The pair is assumed to be coherent.
   static CompileType Create(intptr_t cid, const AbstractType& type);
 
-  CompileType CopyNonNullable() const {
+  // Return the non-nullable version of this type.
+  CompileType CopyNonNullable() {
+    if (IsNull()) {
+      // Represent a non-nullable null type (typically arising for
+      // unreachable values) as None.
+      return None();
+    }
     return CompileType(kNonNullable, kIllegalCid, type_);
   }
 
diff --git a/runtime/vm/compiler/backend/flow_graph.cc b/runtime/vm/compiler/backend/flow_graph.cc
index b5d2201fade..7062a357c4a 100644
--- a/runtime/vm/compiler/backend/flow_graph.cc
+++ b/runtime/vm/compiler/backend/flow_graph.cc
@@ -1559,7 +1559,13 @@ RedefinitionInstr* FlowGraph::EnsureRedefinition(Instruction* prev,
     }
   }
   RedefinitionInstr* redef = new RedefinitionInstr(new Value(original));
-  redef->set_constrained_type(new CompileType(compile_type));
+
+  // Don't set the constrained type when the type is None(), which denotes an
+  // unreachable value (e.g. using value null after an explicit null check).
+  if (!compile_type.IsNone()) {
+    redef->set_constrained_type(new CompileType(compile_type));
+  }
+
   InsertAfter(prev, redef, NULL, FlowGraph::kValue);
   RenameDominatedUses(original, redef, redef);
   return redef;
diff --git a/runtime/vm/compiler/backend/type_propagator.cc b/runtime/vm/compiler/backend/type_propagator.cc
index cb7360eacb2..6e70d926ecb 100644
--- a/runtime/vm/compiler/backend/type_propagator.cc
+++ b/runtime/vm/compiler/backend/type_propagator.cc
@@ -283,7 +283,7 @@ void FlowGraphTypePropagator::VisitCheckClassId(CheckClassIdInstr* check) {
 void FlowGraphTypePropagator::VisitCheckNull(CheckNullInstr* check) {
   Definition* receiver = check->value()->definition();
   CompileType* type = TypeOf(receiver);
-  if (type->is_nullable() && !type->IsNull()) {
+  if (type->is_nullable()) {
     // Insert redefinition for the receiver to guard against invalid
     // code motion.
     EnsureMoreAccurateRedefinition(check, receiver, type->CopyNonNullable());
@@ -305,7 +305,7 @@ void FlowGraphTypePropagator::CheckNonNullSelector(
   if (target.IsNull()) {
     // If the selector is not defined on Null, we can propagate non-nullness.
     CompileType* type = TypeOf(receiver);
-    if (type->is_nullable() && !type->IsNull()) {
+    if (type->is_nullable()) {
       // Insert redefinition for the receiver to guard against invalid
       // code motion.
       EnsureMoreAccurateRedefinition(call, receiver, type->CopyNonNullable());