diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/OverrideResolver.java b/compiler/frontend/src/org/jetbrains/kotlin/resolve/OverrideResolver.java
index e3d9374af1a..ae25e8dcf21 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/OverrideResolver.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/OverrideResolver.java
@@ -28,6 +28,7 @@ import com.intellij.util.containers.MultiMap;
 import com.intellij.util.containers.SmartHashSet;
 import com.intellij.util.containers.hash.EqualityPolicy;
 import kotlin.Unit;
+import kotlin.collections.CollectionsKt;
 import kotlin.jvm.functions.Function1;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -543,6 +544,7 @@ public class OverrideResolver {
 
         int numImplementations = implementations.size();
 
+        // The most common case: there's one implementation in the supertypes with the matching return type
         if (numImplementations == 1 && isReturnTypeOkForOverride(descriptor, implementations.get(0))) return;
 
         List<CallableMemberDescriptor> abstractOverridden = new ArrayList<CallableMemberDescriptor>(allFilteredOverriddenDeclarations.size());
@@ -673,17 +675,14 @@ public class OverrideResolver {
     @NotNull
     private static List<CallableMemberDescriptor> collectAbstractMethodsWithMoreSpecificReturnType(
             @NotNull List<CallableMemberDescriptor> abstractOverridden,
-            @NotNull CallableMemberDescriptor implementation
+            @NotNull final CallableMemberDescriptor implementation
     ) {
-        List<CallableMemberDescriptor> result = new ArrayList<CallableMemberDescriptor>(abstractOverridden.size());
-        for (CallableMemberDescriptor abstractMember : abstractOverridden) {
-            if (!isReturnTypeOkForOverride(abstractMember, implementation)) {
-                result.add(abstractMember);
+        return CollectionsKt.filter(abstractOverridden, new Function1<CallableMemberDescriptor, Boolean>() {
+            @Override
+            public Boolean invoke(@NotNull CallableMemberDescriptor abstractMember) {
+                return !isReturnTypeOkForOverride(abstractMember, implementation);
             }
-        }
-        assert !result.isEmpty() : "Implementation (" + implementation + ") doesn't have the most specific type, " +
-                                   "but none of the other overridden methods does either: " + abstractOverridden;
-        return result;
+        });
     }
 
     @NotNull
diff --git a/compiler/testData/diagnostics/tests/override/kt12482.kt b/compiler/testData/diagnostics/tests/override/kt12482.kt
new file mode 100644
index 00000000000..88e62deef89
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/override/kt12482.kt
@@ -0,0 +1,11 @@
+interface A {
+    fun test(): String = "A"
+}
+
+interface B : A {
+    override fun test(): <!RETURN_TYPE_MISMATCH_ON_OVERRIDE!>Unit<!> = <!TYPE_MISMATCH!>"B"<!>
+}
+
+open class C : A
+
+class D : C(), B
diff --git a/compiler/testData/diagnostics/tests/override/kt12482.txt b/compiler/testData/diagnostics/tests/override/kt12482.txt
new file mode 100644
index 00000000000..03104983ee7
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/override/kt12482.txt
@@ -0,0 +1,31 @@
+package
+
+public interface A {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open fun test(): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface B : A {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ fun test(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public open class C : A {
+    public constructor C()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun test(): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class D : C, B {
+    public constructor D()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun test(): kotlin.String
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
diff --git a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
index 3dd2d147ee7..267de57f91f 100644
--- a/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
+++ b/compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java
@@ -12753,6 +12753,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("kt12482.kt")
+            public void testKt12482() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/override/kt12482.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("kt1862.kt")
             public void testKt1862() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/override/kt1862.kt");