Index: lib/Index/IndexDecl.cpp
===================================================================
--- lib/Index/IndexDecl.cpp
+++ lib/Index/IndexDecl.cpp
@@ -611,18 +611,16 @@
                                            ClassTemplateSpecializationDecl *D) {
     // FIXME: Notify subsequent callbacks if info comes from implicit
     // instantiation.
-    if (D->isThisDeclarationADefinition()) {
-      llvm::PointerUnion<ClassTemplateDecl *,
-                         ClassTemplatePartialSpecializationDecl *>
-          Template = D->getSpecializedTemplateOrPartial();
-      const Decl *SpecializationOf =
-          Template.is<ClassTemplateDecl *>()
-              ? (Decl *)Template.get<ClassTemplateDecl *>()
-              : Template.get<ClassTemplatePartialSpecializationDecl *>();
-      IndexCtx.indexTagDecl(
-          D, SymbolRelation(SymbolRoleSet(SymbolRole::RelationSpecializationOf),
-                            SpecializationOf));
-    }
+    llvm::PointerUnion<ClassTemplateDecl *,
+                       ClassTemplatePartialSpecializationDecl *>
+        Template = D->getSpecializedTemplateOrPartial();
+    const Decl *SpecializationOf =
+        Template.is<ClassTemplateDecl *>()
+            ? (Decl *)Template.get<ClassTemplateDecl *>()
+            : Template.get<ClassTemplatePartialSpecializationDecl *>();
+    IndexCtx.indexTagDecl(
+        D, SymbolRelation(SymbolRoleSet(SymbolRole::RelationSpecializationOf),
+                          SpecializationOf));
     if (TypeSourceInfo *TSI = D->getTypeAsWritten())
       IndexCtx.indexTypeSourceInfo(TSI, /*Parent=*/nullptr,
                                    D->getLexicalDeclContext());
Index: test/Index/Core/index-source.cpp
===================================================================
--- test/Index/Core/index-source.cpp
+++ test/Index/Core/index-source.cpp
@@ -282,7 +282,9 @@
 
 template<>
 class SpecializationDecl<int>;
-// CHECK: [[@LINE-1]]:7 | class(Gen)/C++ | SpecializationDecl | c:@ST>1#T@SpecializationDecl | <no-cgname> | Ref | rel: 0
+// CHECK: [[@LINE-1]]:7 | class(Gen,TS)/C++ | SpecializationDecl | c:@S@SpecializationDecl>#I | <no-cgname> | Decl,RelSpecialization | rel: 1
+// CHECK-NEXT: RelSpecialization | SpecializationDecl | c:@ST>1#T@SpecializationDecl
+// CHECK: [[@LINE-3]]:7 | class(Gen)/C++ | SpecializationDecl | c:@ST>1#T@SpecializationDecl | <no-cgname> | Ref | rel: 0
 
 template<>
 class SpecializationDecl<int> { };
@@ -292,8 +294,10 @@
 
 template<typename T>
 class PartialSpecilizationClass<Cls, T>;
-// CHECK: [[@LINE-1]]:7 | class(Gen)/C++ | PartialSpecilizationClass | c:@ST>2#T#T@PartialSpecilizationClass | <no-cgname> | Ref | rel: 0
-// CHECK-NEXT: [[@LINE-2]]:33 | class/C++ | Cls | c:@S@Cls | <no-cgname> | Ref | rel: 0
+// CHECK: [[@LINE-1]]:7 | class(Gen,TPS)/C++ | PartialSpecilizationClass | c:@SP>1#T@PartialSpecilizationClass>#$@S@Cls#t0.0 | <no-cgname> | Decl,RelSpecialization | rel: 1
+// CHECK-NEXT: RelSpecialization | PartialSpecilizationClass | c:@ST>2#T#T@PartialSpecilizationClass
+// CHECK: [[@LINE-3]]:7 | class(Gen)/C++ | PartialSpecilizationClass | c:@ST>2#T#T@PartialSpecilizationClass | <no-cgname> | Ref | rel: 0
+// CHECK-NEXT: [[@LINE-4]]:33 | class/C++ | Cls | c:@S@Cls | <no-cgname> | Ref | rel: 0
 
 template<>
 class PartialSpecilizationClass<Cls, Cls> : Cls { };