diff --git a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java
index 9652a21e97d..c7d368f361d 100644
--- a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java
+++ b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java
@@ -43118,6 +43118,12 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
                 runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimental.kt");
             }
 
+            @Test
+            @TestMetadata("wasExperimentalCombined.kt")
+            public void testWasExperimentalCombined() throws Exception {
+                runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimentalCombined.kt");
+            }
+
             @Test
             @TestMetadata("wrongTargetsWithoutExplicitTarget.kt")
             public void testWrongTargetsWithoutExplicitTarget() throws Exception {
diff --git a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java
index e27760ec17c..15d15a6ffff 100644
--- a/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java
+++ b/analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java
@@ -43118,6 +43118,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
                 runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimental.kt");
             }
 
+            @Test
+            @TestMetadata("wasExperimentalCombined.kt")
+            public void testWasExperimentalCombined() throws Exception {
+                runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimentalCombined.kt");
+            }
+
             @Test
             @TestMetadata("wrongTargetsWithoutExplicitTarget.kt")
             public void testWrongTargetsWithoutExplicitTarget() throws Exception {
diff --git a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java
index 5a099f9ccb6..c7f4e67c395 100644
--- a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java
@@ -40998,6 +40998,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
                 runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimental.kt");
             }
 
+            @Test
+            @TestMetadata("wasExperimentalCombined.kt")
+            public void testWasExperimentalCombined() throws Exception {
+                runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimentalCombined.kt");
+            }
+
             @Test
             @TestMetadata("wrongTargetsWithoutExplicitTarget.kt")
             public void testWrongTargetsWithoutExplicitTarget() throws Exception {
diff --git a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java
index 7ed673451e7..4bfc83de546 100644
--- a/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java
+++ b/compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java
@@ -41118,6 +41118,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
                 runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimental.kt");
             }
 
+            @Test
+            @TestMetadata("wasExperimentalCombined.kt")
+            public void testWasExperimentalCombined() throws Exception {
+                runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimentalCombined.kt");
+            }
+
             @Test
             @TestMetadata("wrongTargetsWithoutExplicitTarget.kt")
             public void testWrongTargetsWithoutExplicitTarget() throws Exception {
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirSinceKotlinHelpers.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirSinceKotlinHelpers.kt
index 0a7a2d749df..f7aea707dca 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirSinceKotlinHelpers.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirSinceKotlinHelpers.kt
@@ -68,7 +68,6 @@ private fun FirDeclaration.getOwnSinceKotlinVersion(session: FirSession): FirSin
         )
         val apiVersion = ((sinceKotlinSingleArgument as? FirConstExpression<*>)?.value as? String)?.let(ApiVersion.Companion::parse)
         if (apiVersion != null) {
-            // TODO, KT-59825: combine wasExperimentalMarkerClasses in case of several associated declarations with the same maximal API version
             if (result == null || apiVersion > result!!.apiVersion) {
                 result = FirSinceKotlinValue(apiVersion, loadWasExperimentalMarkerClasses(session))
             }
diff --git a/compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimentalCombined.fir.kt b/compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimentalCombined.fir.kt
new file mode 100644
index 00000000000..4879351e0e0
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimentalCombined.fir.kt
@@ -0,0 +1,52 @@
+// API_VERSION: 1.8
+// !DIAGNOSTICS: -INVISIBLE_MEMBER -INVISIBLE_REFERENCE
+
+@RequiresOptIn
+@Retention(AnnotationRetention.BINARY)
+annotation class ClassMarker
+
+@RequiresOptIn
+@Retention(AnnotationRetention.BINARY)
+annotation class ConstructorMarker
+
+@RequiresOptIn
+@Retention(AnnotationRetention.BINARY)
+annotation class TypeAliasMarker
+
+@SinceKotlin("1.9")
+@WasExperimental(ClassMarker::class)
+class C {
+    @SinceKotlin("1.9")
+    @WasExperimental(ConstructorMarker::class)
+    constructor() {}
+}
+
+@SinceKotlin("1.9")
+@WasExperimental(TypeAliasMarker::class)
+typealias T = <!OPT_IN_USAGE_ERROR!>C<!>
+
+@ClassMarker
+fun test1() {
+    <!OPT_IN_USAGE_ERROR!>C<!>()
+}
+
+@ConstructorMarker
+fun test2() {
+    <!OPT_IN_USAGE_ERROR!>C<!>()
+}
+
+@ClassMarker
+@ConstructorMarker
+fun test3() {
+    C()
+}
+
+@ClassMarker
+fun test4(t: <!OPT_IN_USAGE_ERROR!>T<!>) {}
+
+@TypeAliasMarker
+fun test5(t: <!OPT_IN_USAGE_ERROR!>T<!>) {}
+
+@ClassMarker
+@TypeAliasMarker
+fun test6(t: T) {}
diff --git a/compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimentalCombined.kt b/compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimentalCombined.kt
new file mode 100644
index 00000000000..eb2cfa69757
--- /dev/null
+++ b/compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimentalCombined.kt
@@ -0,0 +1,52 @@
+// API_VERSION: 1.8
+// !DIAGNOSTICS: -INVISIBLE_MEMBER -INVISIBLE_REFERENCE
+
+@RequiresOptIn
+@Retention(AnnotationRetention.BINARY)
+annotation class ClassMarker
+
+@RequiresOptIn
+@Retention(AnnotationRetention.BINARY)
+annotation class ConstructorMarker
+
+@RequiresOptIn
+@Retention(AnnotationRetention.BINARY)
+annotation class TypeAliasMarker
+
+@SinceKotlin("1.9")
+@WasExperimental(ClassMarker::class)
+class C {
+    @SinceKotlin("1.9")
+    @WasExperimental(ConstructorMarker::class)
+    constructor() {}
+}
+
+@SinceKotlin("1.9")
+@WasExperimental(TypeAliasMarker::class)
+typealias T = <!OPT_IN_USAGE_ERROR!>C<!>
+
+@ClassMarker
+fun test1() {
+    <!UNRESOLVED_REFERENCE!>C<!>()
+}
+
+@ConstructorMarker
+fun test2() {
+    <!OPT_IN_USAGE_ERROR!>C<!>()
+}
+
+@ClassMarker
+@ConstructorMarker
+fun test3() {
+    C()
+}
+
+@ClassMarker
+fun test4(t: <!OPT_IN_USAGE_ERROR!>T<!>) {}
+
+@TypeAliasMarker
+fun test5(t: <!OPT_IN_USAGE_ERROR!>T<!>) {}
+
+@ClassMarker
+@TypeAliasMarker
+fun test6(t: T) {}
diff --git a/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java b/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java
index 6dc9e4e9d40..4695a5cd1cc 100644
--- a/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java
+++ b/compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java
@@ -43112,6 +43112,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimental.kt");
             }
 
+            @Test
+            @TestMetadata("wasExperimentalCombined.kt")
+            public void testWasExperimentalCombined() throws Exception {
+                runTest("compiler/testData/diagnostics/testsWithStdLib/experimental/wasExperimentalCombined.kt");
+            }
+
             @Test
             @TestMetadata("wrongTargetsWithoutExplicitTarget.kt")
             public void testWrongTargetsWithoutExplicitTarget() throws Exception {