diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirEqualityCompatibilityChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirEqualityCompatibilityChecker.kt
index 9212c8f3a80..e9e7a01784e 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirEqualityCompatibilityChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirEqualityCompatibilityChecker.kt
@@ -19,10 +19,7 @@ import org.jetbrains.kotlin.fir.declarations.utils.isEnumClass
 import org.jetbrains.kotlin.fir.declarations.utils.isFinal
 import org.jetbrains.kotlin.fir.declarations.utils.isInline
 import org.jetbrains.kotlin.fir.declarations.utils.isInterface
-import org.jetbrains.kotlin.fir.expressions.FirEqualityOperatorCall
-import org.jetbrains.kotlin.fir.expressions.FirExpression
-import org.jetbrains.kotlin.fir.expressions.FirOperation
-import org.jetbrains.kotlin.fir.expressions.FirSmartCastExpression
+import org.jetbrains.kotlin.fir.expressions.*
 import org.jetbrains.kotlin.fir.isPrimitiveType
 import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassSymbol
@@ -38,8 +35,8 @@ object FirEqualityCompatibilityChecker : FirEqualityOperatorCallChecker() {
         val arguments = expression.argumentList.arguments
         require(arguments.size == 2) { "Equality operator call with non-2 arguments" }
 
-        val l = arguments[0].toArgumentInfo(context)
-        val r = arguments[1].toArgumentInfo(context)
+        val l = arguments[0].unwrapToMoreUsefulExpression().toArgumentInfo(context)
+        val r = arguments[1].unwrapToMoreUsefulExpression().toArgumentInfo(context)
 
         checkSenselessness(l.smartCastType, r.smartCastType, context, expression, reporter)
 
@@ -81,6 +78,11 @@ object FirEqualityCompatibilityChecker : FirEqualityOperatorCallChecker() {
         }
     }
 
+    private fun FirExpression.unwrapToMoreUsefulExpression() = when (this) {
+        is FirWhenSubjectExpression -> whenRef.value.subject ?: this
+        else -> this
+    }
+
     private fun checkEqualityApplicability(l: TypeInfo, r: TypeInfo, context: CheckerContext): Applicability {
         val oneIsBuiltin = l.isBuiltin || r.isBuiltin
         val oneIsIdentityLess = l.isIdentityLess || r.isIdentityLess
diff --git a/compiler/testData/diagnostics/testsWithStdLib/comparingSmartCastValueToBoolean.fir.kt b/compiler/testData/diagnostics/testsWithStdLib/comparingSmartCastValueToBoolean.fir.kt
index 626a2dee319..1a8dc44e2ea 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/comparingSmartCastValueToBoolean.fir.kt
+++ b/compiler/testData/diagnostics/testsWithStdLib/comparingSmartCastValueToBoolean.fir.kt
@@ -9,7 +9,7 @@ fun foo(a: Any) {
         }
 
         when (a) {
-            <!CONFUSING_BRANCH_CONDITION_ERROR, EQUALITY_NOT_APPLICABLE_WARNING, INCOMPATIBLE_TYPES!>a == 1<!> -> print("1")
+            <!CONFUSING_BRANCH_CONDITION_ERROR, EQUALITY_NOT_APPLICABLE_WARNING, INCOMPATIBLE_TYPES_WARNING!>a == 1<!> -> print("1")
         }
 
         if (<!EQUALITY_NOT_APPLICABLE!>(a <!USELESS_CAST!>as A<!>) == (<!EQUALITY_NOT_APPLICABLE_WARNING!>a == 1<!>)<!>) {
diff --git a/compiler/testData/diagnostics/testsWithStdLib/equalityCompatibilityCommonCases.fir.kt b/compiler/testData/diagnostics/testsWithStdLib/equalityCompatibilityCommonCases.fir.kt
index ea29323b468..5612209d2a5 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/equalityCompatibilityCommonCases.fir.kt
+++ b/compiler/testData/diagnostics/testsWithStdLib/equalityCompatibilityCommonCases.fir.kt
@@ -53,7 +53,7 @@ fun incompatibleTypes(a: Int) = when(a) {
 fun incompatibleTypesSmartCast(a: Any?) {
     if (a is Int) {
         when(a) {
-            <!INCOMPATIBLE_TYPES!>C(10)<!> -> 1
+            <!INCOMPATIBLE_TYPES_WARNING!>C(10)<!> -> 1
             else -> 2
         }
     }