diff --git a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/tasks/AbstractTracingStrategy.java b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/tasks/AbstractTracingStrategy.java
index 513ab1f8ba8..abe78cf1368 100644
--- a/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/tasks/AbstractTracingStrategy.java
+++ b/compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/tasks/AbstractTracingStrategy.java
@@ -23,6 +23,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.lang.descriptors.*;
 import org.jetbrains.jet.lang.psi.*;
 import org.jetbrains.jet.lang.resolve.BindingTrace;
+import org.jetbrains.jet.lang.resolve.DescriptorUtils;
 import org.jetbrains.jet.lang.resolve.calls.inference.*;
 import org.jetbrains.jet.lang.resolve.calls.model.ResolvedCall;
 import org.jetbrains.jet.lang.resolve.descriptorUtil.DescriptorUtilPackage;
@@ -137,19 +138,21 @@ public abstract class AbstractTracingStrategy implements TracingStrategy {
             @NotNull ExplicitReceiverKind explicitReceiverKind
     ) {
         if (explicitReceiverKind == ExplicitReceiverKind.NO_EXPLICIT_RECEIVER) {
-            String qualifiedName;
-            FqName fqName = getFqNameFromTopLevelClass(DescriptorUtilPackage.getImportableDescriptor(classDescriptor));
-            if (reference.getParent() instanceof JetCallableReferenceExpression) {
-                qualifiedName = fqName.parent() + "::" + classDescriptor.getName();
+            DeclarationDescriptor importableDescriptor = DescriptorUtilPackage.getImportableDescriptor(classDescriptor);
+            if (DescriptorUtils.getFqName(importableDescriptor).isSafe()) {
+                FqName fqName = getFqNameFromTopLevelClass(importableDescriptor);
+                String qualifiedName;
+                if (reference.getParent() instanceof JetCallableReferenceExpression) {
+                    qualifiedName = fqName.parent() + "::" + classDescriptor.getName();
+                }
+                else {
+                    qualifiedName = fqName.asString();
+                }
+                trace.report(NESTED_CLASS_SHOULD_BE_QUALIFIED.on(reference, classDescriptor, qualifiedName));
+                return;
             }
-            else {
-                qualifiedName = fqName.asString();
-            }
-            trace.report(NESTED_CLASS_SHOULD_BE_QUALIFIED.on(reference, classDescriptor, qualifiedName));
-        }
-        else {
-            trace.report(NESTED_CLASS_ACCESSED_VIA_INSTANCE_REFERENCE.on(reference, classDescriptor));
         }
+        trace.report(NESTED_CLASS_ACCESSED_VIA_INSTANCE_REFERENCE.on(reference, classDescriptor));
     }
 
     @Override
diff --git a/compiler/testData/diagnostics/tests/inner/kt6026.kt b/compiler/testData/diagnostics/tests/inner/kt6026.kt
new file mode 100644
index 00000000000..e55d6048968
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/inner/kt6026.kt
@@ -0,0 +1,7 @@
+// KT-6026 Exception on instantiating a nested class in an anonymous object
+
+val oo = object {
+    class Nested
+
+    fun f1() = Nested(<!TOO_MANY_ARGUMENTS!>11<!>)
+}
diff --git a/compiler/testData/diagnostics/tests/inner/kt6026.txt b/compiler/testData/diagnostics/tests/inner/kt6026.txt
new file mode 100644
index 00000000000..60695f5c042
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/inner/kt6026.txt
@@ -0,0 +1,3 @@
+package
+
+internal val oo: kotlin.Any
\ No newline at end of file
diff --git a/compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java b/compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java
index 05f0f57aa84..e53ec3a7c4c 100644
--- a/compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java
+++ b/compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java
@@ -5991,6 +5991,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
             
+            @TestMetadata("kt6026.kt")
+            public void testKt6026() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/inner/kt6026.kt");
+                doTest(fileName);
+            }
+            
             @TestMetadata("localClass.kt")
             public void testLocalClass() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/inner/localClass.kt");
diff --git a/idea/idea-analysis/src/org/jetbrains/jet/plugin/libraries/DecompiledNavigationUtils.java b/idea/idea-analysis/src/org/jetbrains/jet/plugin/libraries/DecompiledNavigationUtils.java
index e5a8a3ffd9d..883dee38bfe 100644
--- a/idea/idea-analysis/src/org/jetbrains/jet/plugin/libraries/DecompiledNavigationUtils.java
+++ b/idea/idea-analysis/src/org/jetbrains/jet/plugin/libraries/DecompiledNavigationUtils.java
@@ -29,10 +29,10 @@ import org.jetbrains.jet.lang.resolve.DescriptorUtils;
 import org.jetbrains.jet.lang.resolve.java.PackageClassUtils;
 import org.jetbrains.jet.lang.resolve.kotlin.VirtualFileFinder;
 import org.jetbrains.jet.lang.resolve.name.FqName;
+import org.jetbrains.jet.lang.resolve.name.FqNameUnsafe;
 import org.jetbrains.jet.lang.types.expressions.ExpressionTypingUtils;
 
 import static org.jetbrains.jet.lang.resolve.DescriptorUtils.getFqName;
-import static org.jetbrains.jet.lang.resolve.DescriptorUtils.getFqNameSafe;
 
 public final class DecompiledNavigationUtils {
 
@@ -117,7 +117,8 @@ public final class DecompiledNavigationUtils {
                 || ExpressionTypingUtils.isLocal(containerDescriptor.getContainingDeclaration(), containerDescriptor)) {
                 return getContainerFqName(containerDescriptor.getContainingDeclaration());
             }
-            return getFqNameSafe(containerDescriptor);
+            FqNameUnsafe fqNameUnsafe = getFqName(containerDescriptor);
+            return fqNameUnsafe.isSafe() ? fqNameUnsafe.toSafe() : null;
         }
         return null;
     }