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 afd85c6f00c..9e6b2cec09e 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
@@ -12564,6 +12564,12 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
                 runTest("compiler/testData/diagnostics/tests/generics/localClassTypeRefWithTypeParameterFromFunction.kt");
             }
 
+            @Test
+            @TestMetadata("nullableTypeParameterScope.kt")
+            public void testNullableTypeParameterScope() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/generics/nullableTypeParameterScope.kt");
+            }
+
             @Test
             @TestMetadata("outerTypeParametersInNestedClasses.kt")
             public void testOuterTypeParametersInNestedClasses() 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 2d53c749620..36bed8abf90 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
@@ -12564,6 +12564,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
                 runTest("compiler/testData/diagnostics/tests/generics/localClassTypeRefWithTypeParameterFromFunction.kt");
             }
 
+            @Test
+            @TestMetadata("nullableTypeParameterScope.kt")
+            public void testNullableTypeParameterScope() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/generics/nullableTypeParameterScope.kt");
+            }
+
             @Test
             @TestMetadata("outerTypeParametersInNestedClasses.kt")
             public void testOuterTypeParametersInNestedClasses() 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 d989a995887..29701d5bd17 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
@@ -12564,6 +12564,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
                 runTest("compiler/testData/diagnostics/tests/generics/localClassTypeRefWithTypeParameterFromFunction.kt");
             }
 
+            @Test
+            @TestMetadata("nullableTypeParameterScope.kt")
+            public void testNullableTypeParameterScope() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/generics/nullableTypeParameterScope.kt");
+            }
+
             @Test
             @TestMetadata("outerTypeParametersInNestedClasses.kt")
             public void testOuterTypeParametersInNestedClasses() 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 d1354f5c8c6..b02311885f1 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
@@ -12570,6 +12570,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
                 runTest("compiler/testData/diagnostics/tests/generics/localClassTypeRefWithTypeParameterFromFunction.kt");
             }
 
+            @Test
+            @TestMetadata("nullableTypeParameterScope.kt")
+            public void testNullableTypeParameterScope() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/generics/nullableTypeParameterScope.kt");
+            }
+
             @Test
             @TestMetadata("outerTypeParametersInNestedClasses.kt")
             public void testOuterTypeParametersInNestedClasses() throws Exception {
diff --git a/compiler/fir/providers/src/org/jetbrains/kotlin/fir/resolve/substitution/Substitutors.kt b/compiler/fir/providers/src/org/jetbrains/kotlin/fir/resolve/substitution/Substitutors.kt
index ae94f6f689b..54b9c67037f 100644
--- a/compiler/fir/providers/src/org/jetbrains/kotlin/fir/resolve/substitution/Substitutors.kt
+++ b/compiler/fir/providers/src/org/jetbrains/kotlin/fir/resolve/substitution/Substitutors.kt
@@ -173,7 +173,7 @@ abstract class AbstractConeSubstitutor(protected val typeContext: ConeTypeContex
 fun substitutorByMap(substitution: Map<FirTypeParameterSymbol, ConeKotlinType>, useSiteSession: FirSession): ConeSubstitutor {
     // If all arguments match parameters, then substitutor isn't needed
     if (substitution.all { (parameterSymbol, argumentType) ->
-            (argumentType as? ConeTypeParameterType)?.lookupTag?.typeParameterSymbol == parameterSymbol
+            (argumentType as? ConeTypeParameterType)?.lookupTag?.typeParameterSymbol == parameterSymbol && !argumentType.isMarkedNullable
         }
     ) return ConeSubstitutor.Empty
     return ConeSubstitutorByMap(substitution, useSiteSession)
diff --git a/compiler/testData/diagnostics/tests/generics/nullableTypeParameterScope.kt b/compiler/testData/diagnostics/tests/generics/nullableTypeParameterScope.kt
new file mode 100644
index 00000000000..848601eb4df
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/generics/nullableTypeParameterScope.kt
@@ -0,0 +1,11 @@
+// FIR_IDENTICAL
+// ISSUE: KT-57001
+
+interface ConverterFromString<T> {
+
+    fun ofS(s: String): T
+
+    fun nullable(nullText: String): ConverterFromString<T?> = object: ConverterFromString<T?> {
+        override fun ofS(s: String): T? = if (s == nullText) null else this@ConverterFromString.ofS(s)
+    }
+}
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 22622a1044d..48c59bb8afe 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
@@ -12570,6 +12570,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/generics/localClassTypeRefWithTypeParameterFromFunction.kt");
             }
 
+            @Test
+            @TestMetadata("nullableTypeParameterScope.kt")
+            public void testNullableTypeParameterScope() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/generics/nullableTypeParameterScope.kt");
+            }
+
             @Test
             @TestMetadata("outerTypeParametersInNestedClasses.kt")
             public void testOuterTypeParametersInNestedClasses() throws Exception {