diff --git a/compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/extensionReceiver.kt b/compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/extensionReceiver.kt
new file mode 100644
index 00000000000..f34b254d12c
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/extensionReceiver.kt
@@ -0,0 +1,38 @@
+// !LANGUAGE: +AllowContractsForCustomFunctions +UseReturnsEffect
+// !USE_EXPERIMENTAL: kotlin.contracts.ExperimentalContracts
+// !DIAGNOSTICS: -INVISIBLE_REFERENCE -INVISIBLE_MEMBER
+//
+// ISSUE: KT-28672
+
+import kotlin.contracts.*
+
+fun CharSequence?.isNullOrEmpty(): Boolean {
+    contract {
+        returns(false) implies (this@isNullOrEmpty != null)
+    }
+
+    return this == null || <!DEBUG_INFO_SMARTCAST!>this<!>.length == 0
+}
+
+fun smartcastOnReceiver(s: String?) {
+    with(s) {
+        if (isNullOrEmpty()) {
+            <!UNSAFE_CALL!>length<!>
+        }
+        else {
+            <!UNSAFE_CALL!>length<!>
+        }
+    }
+}
+
+fun mixedReceiver(s: String?) {
+    if (!s.isNullOrEmpty()) {
+        with(<!DEBUG_INFO_SMARTCAST!>s<!>) {
+            length
+        }
+    } else {
+        with(s) {
+            <!UNSAFE_CALL!>length<!>
+        }
+    }
+}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/extensionReceiver.txt b/compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/extensionReceiver.txt
new file mode 100644
index 00000000000..04bbccbbcac
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/extensionReceiver.txt
@@ -0,0 +1,7 @@
+package
+
+public fun mixedReceiver(/*0*/ s: kotlin.String?): kotlin.Unit
+public fun smartcastOnReceiver(/*0*/ s: kotlin.String?): kotlin.Unit
+public fun kotlin.CharSequence?.isNullOrEmpty(): kotlin.Boolean
+    Returns(FALSE) -> <this> != null
+
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithStdLibGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithStdLibGenerated.java
index 1396a91de58..a913f6217a8 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithStdLibGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestWithStdLibGenerated.java
@@ -1296,6 +1296,11 @@ public class DiagnosticsTestWithStdLibGenerated extends AbstractDiagnosticsTestW
                 runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/deeplyNested.kt");
             }
 
+            @TestMetadata("extensionReceiver.kt")
+            public void testExtensionReceiver() throws Exception {
+                runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/extensionReceiver.kt");
+            }
+
             @TestMetadata("intersectingInfo.kt")
             public void testIntersectingInfo() throws Exception {
                 runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/intersectingInfo.kt");
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsTestWithStdLibUsingJavacGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsTestWithStdLibUsingJavacGenerated.java
index c91ce0013c5..990b63e6031 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsTestWithStdLibUsingJavacGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsTestWithStdLibUsingJavacGenerated.java
@@ -1296,6 +1296,11 @@ public class DiagnosticsTestWithStdLibUsingJavacGenerated extends AbstractDiagno
                 runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/deeplyNested.kt");
             }
 
+            @TestMetadata("extensionReceiver.kt")
+            public void testExtensionReceiver() throws Exception {
+                runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/extensionReceiver.kt");
+            }
+
             @TestMetadata("intersectingInfo.kt")
             public void testIntersectingInfo() throws Exception {
                 runTest("compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/intersectingInfo.kt");