diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/BindingContext.java b/compiler/frontend/src/org/jetbrains/kotlin/resolve/BindingContext.java
index 5d88ede8299..a3251f5159c 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/BindingContext.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/BindingContext.java
@@ -51,6 +51,7 @@ import java.util.Collections;
 
 import static org.jetbrains.kotlin.util.slicedMap.RewritePolicy.DO_NOTHING;
 import static org.jetbrains.kotlin.util.slicedMap.Slices.COMPILE_TIME_VALUE_REWRITE_POLICY;
+import static org.jetbrains.kotlin.util.slicedMap.Slices.CONSERVATIVE_SET_INCLUSION_SEMANTICS;
 
 public interface BindingContext {
     BindingContext EMPTY = new BindingContext() {
@@ -179,7 +180,7 @@ public interface BindingContext {
     WritableSlice<KtExpression, Boolean> PROCESSED = Slices.createSimpleSlice();
     // Please do not use this slice (USED_AS_EXPRESSION) directly,
     // use extension element.isUsedAsExpression() instead
-    WritableSlice<KtElement, Boolean> USED_AS_EXPRESSION = Slices.createSimpleSetSlice();
+    WritableSlice<KtElement, Boolean> USED_AS_EXPRESSION = new BasicWritableSlice<>(CONSERVATIVE_SET_INCLUSION_SEMANTICS);
     WritableSlice<KtElement, Boolean> USED_AS_RESULT_OF_LAMBDA = Slices.createSimpleSetSlice();
 
     WritableSlice<VariableDescriptor, CaptureKind> CAPTURED_IN_CLOSURE = new BasicWritableSlice<>(DO_NOTHING);
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/bindingContextUtil/BindingContextUtils.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/bindingContextUtil/BindingContextUtils.kt
index 6a24b78e4f0..b3e15cbbbaf 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/bindingContextUtil/BindingContextUtils.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/bindingContextUtil/BindingContextUtils.kt
@@ -57,11 +57,7 @@ fun KtReturnExpression.getTargetFunction(context: BindingContext): KtCallableDec
 }
 
 fun KtExpression.isUsedAsExpression(context: BindingContext): Boolean =
-    context[USED_AS_EXPRESSION, this]
-        ?: throw AssertionError(
-            "BindingContext returned null for Boolean slice: " +
-                    if (context == EMPTY) "BindingContext.EMPTY" else context.javaClass.toString()
-        )
+    context[USED_AS_EXPRESSION, this] ?: false
 
 fun KtExpression.isUsedAsResultOfLambda(context: BindingContext): Boolean = context[USED_AS_RESULT_OF_LAMBDA, this]!!
 fun KtExpression.isUsedAsStatement(context: BindingContext): Boolean = !isUsedAsExpression(context)
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/util/slicedMap/Slices.java b/compiler/frontend/src/org/jetbrains/kotlin/util/slicedMap/Slices.java
index 494434aef08..4b7d8b99120 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/util/slicedMap/Slices.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/util/slicedMap/Slices.java
@@ -80,6 +80,24 @@ public class Slices {
         }
     };
 
+    // For Boolean-valued slices modelling set-membership, this policy
+    // implements constructing a set by element-wise inclusion, conservatively:
+    // allow rewriting false->true but not true->false.
+    //
+    // Used in growing the set of `USED_AS_EXPRESSION` in CFG analysis.
+    public static final RewritePolicy CONSERVATIVE_SET_INCLUSION_SEMANTICS = new RewritePolicy() {
+        @Override
+        public <K> boolean rewriteProcessingNeeded(K key) {
+            return true;
+        }
+
+        @Override
+        public <K, V> boolean processRewrite(WritableSlice<K, V> slice, K key, V oldValue, V newValue) {
+            assert (newValue instanceof Boolean);
+            return (Boolean)newValue;
+        }
+    };
+
     private Slices() {
     }
 
diff --git a/compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/BranchingExpressionGenerator.kt b/compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/BranchingExpressionGenerator.kt
index da3dbbde25c..ab11928b8fa 100644
--- a/compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/BranchingExpressionGenerator.kt
+++ b/compiler/ir/ir.psi2ir/src/org/jetbrains/kotlin/psi2ir/generators/BranchingExpressionGenerator.kt
@@ -32,6 +32,7 @@ import org.jetbrains.kotlin.psi.psiUtil.startOffsetSkippingComments
 import org.jetbrains.kotlin.psi2ir.deparenthesize
 import org.jetbrains.kotlin.psi2ir.intermediate.loadAt
 import org.jetbrains.kotlin.resolve.BindingContext
+import org.jetbrains.kotlin.resolve.bindingContextUtil.isUsedAsExpression
 import org.jetbrains.kotlin.utils.SmartList
 
 class BranchingExpressionGenerator(statementGenerator: StatementGenerator) : StatementGeneratorExtension(statementGenerator) {
@@ -142,7 +143,7 @@ class BranchingExpressionGenerator(statementGenerator: StatementGenerator) : Sta
     }
 
     private fun addElseBranchForExhaustiveWhenIfNeeded(irWhen: IrWhen, whenExpression: KtWhenExpression) {
-        val isUsedAsExpression = true == get(BindingContext.USED_AS_EXPRESSION, whenExpression)
+        val isUsedAsExpression = whenExpression.isUsedAsExpression(context.bindingContext)
         val isImplicitElseRequired =
             if (isUsedAsExpression)
                 true == get(BindingContext.EXHAUSTIVE_WHEN, whenExpression)