diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzer.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzer.kt
index 2f8008b59da..2ab621e7eb6 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzer.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/dfa/FirDataFlowAnalyzer.kt
@@ -619,7 +619,14 @@ abstract class FirDataFlowAnalyzer<FLOW : Flow>(
                         lastNode.flow,
                         argumentVariable,
                         functionCallVariable,
-                        filter = { it.condition.operation == value.toOperation() }
+                        filter = { it.condition.operation == Operation.EqTrue },
+                        transform = {
+                            when (value) {
+                                ConeBooleanConstantReference.TRUE -> it
+                                ConeBooleanConstantReference.FALSE -> it.invertCondition()
+                                else -> throw IllegalStateException()
+                            }
+                        }
                     )
                 }
 
diff --git a/compiler/fir/resolve/testData/resolveWithStdlib/contracts/notIsNullOrEmpty.kt b/compiler/fir/resolve/testData/resolveWithStdlib/contracts/notIsNullOrEmpty.kt
new file mode 100644
index 00000000000..4a615ff5aa3
--- /dev/null
+++ b/compiler/fir/resolve/testData/resolveWithStdlib/contracts/notIsNullOrEmpty.kt
@@ -0,0 +1,14 @@
+fun test_1(s: String?) {
+    when {
+        !s.isNullOrEmpty() -> s.length // Should be OK
+    }
+}
+
+fun test_2(s: String?) {
+    // contracts related
+    if (s.isNullOrEmpty()) {
+        s.<!INAPPLICABLE_CANDIDATE!>length<!> // Should be bad
+    } else {
+        s.length // Should be OK
+    }
+}
diff --git a/compiler/fir/resolve/testData/resolveWithStdlib/contracts/notIsNullOrEmpty.txt b/compiler/fir/resolve/testData/resolveWithStdlib/contracts/notIsNullOrEmpty.txt
new file mode 100644
index 00000000000..0f5bdfb67c4
--- /dev/null
+++ b/compiler/fir/resolve/testData/resolveWithStdlib/contracts/notIsNullOrEmpty.txt
@@ -0,0 +1,20 @@
+FILE: notIsNullOrEmpty.kt
+    public final fun test_1(s: R|kotlin/String?|): R|kotlin/Unit| {
+        when () {
+            R|<local>/s|.R|kotlin/text/isNullOrEmpty|().R|kotlin/Boolean.not|() ->  {
+                R|<local>/s|.R|kotlin/String.length|
+            }
+        }
+
+    }
+    public final fun test_2(s: R|kotlin/String?|): R|kotlin/Unit| {
+        when () {
+            R|<local>/s|.R|kotlin/text/isNullOrEmpty|() ->  {
+                R|<local>/s|.<Inapplicable(WRONG_RECEIVER): [kotlin/String.length]>#
+            }
+            else ->  {
+                R|<local>/s|.R|kotlin/String.length|
+            }
+        }
+
+    }
diff --git a/compiler/fir/resolve/testData/resolveWithStdlib/problems/complexSmartCasts.kt b/compiler/fir/resolve/testData/resolveWithStdlib/problems/complexSmartCasts.kt
index feeb5f29c34..c77ab4db826 100644
--- a/compiler/fir/resolve/testData/resolveWithStdlib/problems/complexSmartCasts.kt
+++ b/compiler/fir/resolve/testData/resolveWithStdlib/problems/complexSmartCasts.kt
@@ -1,10 +1,3 @@
-fun test_1(s: String?) {
-    // contracts related
-    when {
-        !s.isNullOrEmpty() -> s.<!INAPPLICABLE_CANDIDATE!>length<!> // Should be OK
-    }
-}
-
 fun test_2(s: String?) {
     s?.let {
         takeString(it) // Should be OK
diff --git a/compiler/fir/resolve/testData/resolveWithStdlib/problems/complexSmartCasts.txt b/compiler/fir/resolve/testData/resolveWithStdlib/problems/complexSmartCasts.txt
index 326bda59e4d..7d089d28cb7 100644
--- a/compiler/fir/resolve/testData/resolveWithStdlib/problems/complexSmartCasts.txt
+++ b/compiler/fir/resolve/testData/resolveWithStdlib/problems/complexSmartCasts.txt
@@ -1,12 +1,4 @@
 FILE: complexSmartCasts.kt
-    public final fun test_1(s: R|kotlin/String?|): R|kotlin/Unit| {
-        when () {
-            R|<local>/s|.R|kotlin/text/isNullOrEmpty|().R|kotlin/Boolean.not|() ->  {
-                R|<local>/s|.<Inapplicable(WRONG_RECEIVER): [kotlin/String.length]>#
-            }
-        }
-
-    }
     public final fun test_2(s: R|kotlin/String?|): R|kotlin/Unit| {
         R|<local>/s|?.R|kotlin/let|<R|kotlin/String|, R|kotlin/Unit|>(<L> = let@fun <anonymous>(it: R|kotlin/String|): R|kotlin/Unit| <kind=EXACTLY_ONCE>  {
             R|/takeString|(R|<local>/it|)
diff --git a/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirDiagnosticsWithStdlibTestGenerated.java b/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirDiagnosticsWithStdlibTestGenerated.java
index e3a93393d4e..94c422e8628 100644
--- a/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirDiagnosticsWithStdlibTestGenerated.java
+++ b/compiler/fir/resolve/tests/org/jetbrains/kotlin/fir/FirDiagnosticsWithStdlibTestGenerated.java
@@ -475,6 +475,11 @@ public class FirDiagnosticsWithStdlibTestGenerated extends AbstractFirDiagnostic
         public void testConditionalEffects() throws Exception {
             runTest("compiler/fir/resolve/testData/resolveWithStdlib/contracts/conditionalEffects.kt");
         }
+
+        @TestMetadata("notIsNullOrEmpty.kt")
+        public void testNotIsNullOrEmpty() throws Exception {
+            runTest("compiler/fir/resolve/testData/resolveWithStdlib/contracts/notIsNullOrEmpty.kt");
+        }
     }
 
     @TestMetadata("compiler/fir/resolve/testData/resolveWithStdlib/inference")
diff --git a/compiler/testData/diagnostics/testsWithStdLib/contracts/fromStdlib/isNullOrBlank.fir.kt b/compiler/testData/diagnostics/testsWithStdLib/contracts/fromStdlib/isNullOrBlank.fir.kt
index 40960b5b21e..443bdf08694 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/contracts/fromStdlib/isNullOrBlank.fir.kt
+++ b/compiler/testData/diagnostics/testsWithStdLib/contracts/fromStdlib/isNullOrBlank.fir.kt
@@ -6,13 +6,13 @@ fun testIsNullOrBlank(x: String?) {
         x.<!INAPPLICABLE_CANDIDATE!>length<!>
     }
     else {
-        x.<!INAPPLICABLE_CANDIDATE!>length<!>
+        x.length
     }
 }
 
 fun testIsNotNullOrBlank(x: String?) {
     if (!x.isNullOrBlank()) {
-        x.<!INAPPLICABLE_CANDIDATE!>length<!>
+        x.length
     }
 
     x.<!INAPPLICABLE_CANDIDATE!>length<!>
diff --git a/compiler/testData/diagnostics/testsWithStdLib/contracts/fromStdlib/isNullOrEmpty.fir.kt b/compiler/testData/diagnostics/testsWithStdLib/contracts/fromStdlib/isNullOrEmpty.fir.kt
index f33d9520b95..c096243d0a9 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/contracts/fromStdlib/isNullOrEmpty.fir.kt
+++ b/compiler/testData/diagnostics/testsWithStdLib/contracts/fromStdlib/isNullOrEmpty.fir.kt
@@ -6,13 +6,13 @@ fun testIsNullOrEmpty(x: String?) {
         x.<!INAPPLICABLE_CANDIDATE!>length<!>
     }
     else {
-        x.<!INAPPLICABLE_CANDIDATE!>length<!>
+        x.length
     }
 }
 
 fun testIsNotNullOrEmpty(x: String?) {
     if (!x.isNullOrEmpty()) {
-        x.<!INAPPLICABLE_CANDIDATE!>length<!>
+        x.length
     }
 
     x.<!INAPPLICABLE_CANDIDATE!>length<!>