diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/AccessContext.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/AccessContext.java
index 4b111b51fa8..ae20e9dc72e 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/AccessContext.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/AccessContext.java
@@ -18,6 +18,7 @@ import org.eclipse.cdt.core.dom.ast.IASTNode;
 import org.eclipse.cdt.core.dom.ast.IBinding;
 import org.eclipse.cdt.core.dom.ast.ICompositeType;
 import org.eclipse.cdt.core.dom.ast.IProblemBinding;
+import org.eclipse.cdt.core.dom.ast.IType;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPAliasTemplateInstance;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPBase;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPClassScope;
@@ -33,6 +34,7 @@ import org.eclipse.cdt.core.dom.ast.cpp.ICPPTemplateParameter;
 import org.eclipse.cdt.core.parser.util.ArrayUtil;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.ClassTypeHelper;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.ICPPDeferredClassInstance;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.ICPPInternalUnknownScope;
 
 /**
  * The context that determines access to private and protected class members.
@@ -236,6 +238,9 @@ public class AccessContext {
 		if (bases != null) {
 			for (ICPPBase base : bases) {
 				IBinding baseClass = base.getBaseClass();
+				if (baseClass instanceof ICPPDeferredClassInstance) {
+					baseClass = ((ICPPDeferredClassInstance) baseClass).getTemplateDefinition();
+				}
 				if (!(baseClass instanceof ICPPClassType)) {
 					continue;
 				}
@@ -254,9 +259,16 @@ public class AccessContext {
 		LookupData data = new LookupData(name);
 		isUnqualifiedLookup= !data.qualified;
 		
-		ICPPScope scope= CPPSemantics.getLookupScope(name);
+		ICPPScope scope = CPPSemantics.getLookupScope(name);
 		while (scope != null && !(scope instanceof ICPPClassScope)) {
-			scope = CPPSemantics.getParentScope(scope, data.getTranslationUnit());
+			if (scope instanceof ICPPInternalUnknownScope) {
+				IType scopeType = ((ICPPInternalUnknownScope) scope).getScopeType();
+				if (scopeType instanceof ICPPDeferredClassInstance) {
+					return ((ICPPDeferredClassInstance) scopeType).getClassTemplate();
+				}
+			} else {
+				scope = CPPSemantics.getParentScope(scope, data.getTranslationUnit());
+			}
 		}
 		if (scope instanceof ICPPClassScope) {
 			return ((ICPPClassScope) scope).getClassType();
diff --git a/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/contentassist2/CompletionTests.java b/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/contentassist2/CompletionTests.java
index d6663d6a837..4c94e10651b 100644
--- a/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/contentassist2/CompletionTests.java
+++ b/core/org.eclipse.cdt.ui.tests/ui/org/eclipse/cdt/ui/tests/text/contentassist2/CompletionTests.java
@@ -743,7 +743,7 @@ public class CompletionTests extends AbstractContentAssistTest {
 	//			using TParam = T;
 	//		};
 	//	};
-	//	
+	//
 	//	struct NestingTest: Parent<int> {
 	//		struct A : Nested {
 	//			TP/*cursor*/
@@ -754,6 +754,24 @@ public class CompletionTests extends AbstractContentAssistTest {
 		assertCompletionResults(fCursorOffset, expected, ID);
 	}
 
+	//	template<typename T>
+	//	class Parent {
+	//		struct NestedHidden {};
+	//	protected:
+	//		struct NestedProtected {};
+	//	public:
+	//		struct NestedPublic {};
+	//	};
+	//
+	//	template<typename T>
+	//	class NestingTest: Parent<T> {
+	//		Parent<T>::/*cursor*/
+	//	};
+	public void testNestedBaseTemplateMembersFromUnknownScope_456752() throws Exception {
+		final String[] expected = { "NestedProtected", "NestedPublic" };
+		assertCompletionResults(fCursorOffset, expected, ID);
+	}
+
 	//	struct A {};
 	//
 	//	template<typename T>