Index: clang-tidy/modernize/UseDefaultCheck.cpp
===================================================================
--- clang-tidy/modernize/UseDefaultCheck.cpp
+++ clang-tidy/modernize/UseDefaultCheck.cpp
@@ -241,6 +241,7 @@
   if (SpecialFunctionDecl->isDeleted() ||
       SpecialFunctionDecl->isExplicitlyDefaulted() ||
       SpecialFunctionDecl->isLateTemplateParsed() ||
+      SpecialFunctionDecl->isTemplateInstantiation() ||
       !SpecialFunctionDecl->isUserProvided() || !SpecialFunctionDecl->hasBody())
     return;
 
Index: test/clang-tidy/modernize-use-default.cpp
===================================================================
--- test/clang-tidy/modernize-use-default.cpp
+++ test/clang-tidy/modernize-use-default.cpp
@@ -124,6 +124,26 @@
   // CHECK-FIXES: ~Temp() = default;
 };
 
+// Class template out of line with explicit instantiation.
+template <class T>
+class TempODef {
+public:
+  TempODef();
+  ~TempODef();
+};
+
+template <class T>
+TempODef<T>::TempODef() {}
+// CHECK-MESSAGES: :[[@LINE-2]]:1: warning: use '= default'
+// CHECK-FIXES: TempODef<T>::TempODef() = default;
+template <class T>
+TempODef<T>::~TempODef() {}
+// CHECK-MESSAGES: :[[@LINE-2]]:1: warning: use '= default'
+// CHECK-FIXES: TempODef<T>::~TempODef() = default;
+
+template class TempODef<int>;
+template class TempODef<double>;
+
 // Non user-provided constructor/destructor.
 struct Imp {
   int Int;