diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 8b6232a6b9e6f..7086d337304b1 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -391,6 +391,10 @@ Bug Fixes in This Version
   at the point where it is required. This fixes:
   (`#62224 <https://github.com/llvm/llvm-project/issues/62224>`_) and
   (`#62596 <https://github.com/llvm/llvm-project/issues/62596>`_)
+- Fix an assertion when instantiating the body of a Class Template Specialization
+  when it had been instantiated from a partial template specialization with different
+  template arguments on the containing class. This fixes:
+  (`#60778 <https://github.com/llvm/llvm-project/issues/60778>`_).
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index 3d5da5f8d8284..32a8ba1a5c46d 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -163,6 +163,14 @@ HandleClassTemplateSpec(const ClassTemplateSpecializationDecl *ClassTemplSpec,
     assert(ClassTemplSpec->getSpecializedTemplate() && "No class template?");
     if (ClassTemplSpec->getSpecializedTemplate()->isMemberSpecialization())
       return Response::Done();
+
+    // If this was instantiated from a partial template specialization, we need
+    // to get the next level of declaration context from the partial
+    // specialization, as the ClassTemplateSpecializationDecl's
+    // DeclContext/LexicalDeclContext will be for the primary template.
+    if (auto *InstFromPartialTempl = ClassTemplSpec->getSpecializedTemplateOrPartial()
+                      .dyn_cast<ClassTemplatePartialSpecializationDecl *>())
+      return Response::ChangeDecl(InstFromPartialTempl->getLexicalDeclContext());
   }
   return Response::UseNextDecl(ClassTemplSpec);
 }
diff --git a/clang/test/SemaTemplate/partial-spec-instantiate.cpp b/clang/test/SemaTemplate/partial-spec-instantiate.cpp
index 369ff69aa3756..c457c03baba0f 100644
--- a/clang/test/SemaTemplate/partial-spec-instantiate.cpp
+++ b/clang/test/SemaTemplate/partial-spec-instantiate.cpp
@@ -134,3 +134,23 @@ namespace IgnorePartialSubstitution {
 
   _Static_assert(S::value, "");
 }
+
+namespace GH60778 {
+  template <bool B = false> class ClassTemplate {
+  public:
+      template <typename T, typename = void> class Nested {};
+  };
+
+  template <typename DerivedType> class Base {};
+
+  template <>
+  template <typename T>
+  class ClassTemplate<>::Nested<T> : public Base<ClassTemplate<>::Nested<T> > {};
+
+  void use() {
+    // This should instantiate the body of Nested with the template arguments
+    // from the Partial Specialization. This would previously get confused and
+    // get the template arguments from the primary template instead.
+    ClassTemplate<>::Nested<int> instantiation;
+  }
+}