diff --git a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java
index fa80afde3a1..c1f8b07fbed 100644
--- a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java
+++ b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/AST2TemplateTests.java
@@ -10557,7 +10557,23 @@ public class AST2TemplateTests extends AST2CPPTestBase {
 	//
 	//	template <int... I>
 	//	void foo(index_sequence<I...>);
-	public void testTemplateAliasWithVariadicNonTypeArgs_530086() throws Exception {
+	public void testTemplateAliasWithVariadicNonTypeArgs_530086a() throws Exception {
+		parseAndCheckBindings();
+	}
+	
+	//	template <int...>
+	//	struct integer_sequence {};
+	//
+	//	template <int... I>
+	//	using index_sequence = integer_sequence<I...>;
+	//
+	//	template <typename, int... I>
+	//	void bar(index_sequence<I...>);
+	//	 
+	//	void foo() {
+	//	    bar<int>(integer_sequence<0>{});
+	//	}
+	public void testTemplateAliasWithVariadicArgs_530086b() throws Exception {
 		parseAndCheckBindings();
 	}
 }
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java
index b4915bb19c2..3ac22c11d96 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/CPPTemplates.java
@@ -222,7 +222,7 @@ public class CPPTemplates {
 
 	// Used to indicate that two different packs with different sizes were found.
 	static final int PACK_SIZE_FAIL = -2;
-
+	
 	// Used to indicate that no template parameter packs were found.
 	static final int PACK_SIZE_NOT_FOUND = Integer.MAX_VALUE;
 
@@ -1224,14 +1224,6 @@ public class CPPTemplates {
 		if (tpar.isParameterPack()) {
 			ICPPTemplateArgument[] args= tpMap.getPackExpansion(tpar);
 			if (args != null) {
-				// The arguments could be dependent, so they could themselves
-				// contain pack expansions.
-				for (ICPPTemplateArgument arg : args) {
-					if (arg.isPackExpansion()) {
-						return PACK_SIZE_DEFER;
-					}
-				}
-				
 				return args.length;
 			}
 			return PACK_SIZE_DEFER;
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/EvalUnaryTypeID.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/EvalUnaryTypeID.java
index 41ff79f4ebe..2e3beb57384 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/EvalUnaryTypeID.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/semantics/EvalUnaryTypeID.java
@@ -43,6 +43,8 @@ import org.eclipse.cdt.core.dom.ast.IASTNode;
 import org.eclipse.cdt.core.dom.ast.IBinding;
 import org.eclipse.cdt.core.dom.ast.IType;
 import org.eclipse.cdt.core.dom.ast.IValue;
+import org.eclipse.cdt.core.dom.ast.cpp.ICPPTemplateArgument;
+import org.eclipse.cdt.core.dom.ast.cpp.ICPPTemplateParameter;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPTemplateParameterMap;
 import org.eclipse.cdt.internal.core.dom.parser.DependentValue;
 import org.eclipse.cdt.internal.core.dom.parser.ITypeMarshalBuffer;
@@ -208,17 +210,9 @@ public class EvalUnaryTypeID extends CPPDependentEvaluation {
 	@Override
 	public ICPPEvaluation instantiate(InstantiationContext context, int maxDepth) {
 		if (fOperator == op_sizeofParameterPack) {
-			int packSize = determinePackSize(context.getParameterMap());
-			if (packSize == CPPTemplates.PACK_SIZE_FAIL || packSize == CPPTemplates.PACK_SIZE_NOT_FOUND) {
-				return EvalFixed.INCOMPLETE;
-			} else if (packSize != CPPTemplates.PACK_SIZE_DEFER) {
-				return new EvalFixed(getType(), getValueCategory(), IntegralValue.create(packSize));
-			}
+			return instantiateSizeofParameterPack(context);
 		}
-		IType type = CPPTemplates.instantiateType(fOrigType, context);
-		if (type == fOrigType)
-			return this;
-		return new EvalUnaryTypeID(fOperator, type, getTemplateDefinition());
+		return instantiateBySubstitution(context);
 	}
 
 	@Override
@@ -235,4 +229,49 @@ public class EvalUnaryTypeID extends CPPDependentEvaluation {
 	public boolean referencesTemplateParameter() {
 		return CPPTemplates.isDependentType(fOrigType);
 	}
+	
+	private ICPPEvaluation instantiateBySubstitution(InstantiationContext context) {
+		IType type = CPPTemplates.instantiateType(fOrigType, context);
+		if (type == fOrigType)
+			return this;
+		return new EvalUnaryTypeID(fOperator, type, getTemplateDefinition());
+	}
+	
+	private ICPPEvaluation instantiateSizeofParameterPack(InstantiationContext context) {
+		if (fOrigType instanceof ICPPTemplateParameter) {
+			ICPPTemplateParameter pack = (ICPPTemplateParameter) fOrigType;
+			if (pack.isParameterPack()) {
+				ICPPTemplateArgument[] args = context.getPackExpansion(pack);
+				if (args == null) {
+					return this;
+				}
+				int concreteArgCount = 0;
+				boolean havePackExpansion = false;
+				for (ICPPTemplateArgument arg : args) {
+					if (arg.isPackExpansion()) {
+						havePackExpansion = true;
+					} else {
+						concreteArgCount++;
+					}
+				}
+				if (havePackExpansion) {
+					// TODO(bug 530103): 
+					//   This will only handle correctly the case where there is a single argument
+					//   which is a pack expansion, and no concrete arguments.
+					//   To correctly handle cases with multiple pack expansions, or a mixture
+					//   of concrete arguments and pack expansions, we need to do the following:
+					//     - For each pack expansion, find the parameter pack P which it's
+					//       expanding (if it's expanding multiple parameter packs, any one
+					//       should be sufficient), and construct an EvalUnaryTypeId representing 
+					//       sizeof...(P).
+					//     - Construct an EvalBinary tree representing the sum of |concreteArgCount|
+					//       and the EvalUnaryTypeIds from the previous step.
+					return instantiateBySubstitution(context);
+				} else {
+					return new EvalFixed(getType(), getValueCategory(), IntegralValue.create(concreteArgCount));
+				}
+			}
+		}
+		return EvalFixed.INCOMPLETE;
+	}
 }