Index: clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp
+++ clang-tools-extra/clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp
@@ -297,6 +297,10 @@
     // Skip declarations delayed by late template parsing without a body.
     if (!Ctor->getBody())
       return;
+    // Skip out-of-band explicitly defaulted special member functions
+    // (except the default constructor).
+    if (Ctor->isExplicitlyDefaulted() && !Ctor->isDefaultConstructor())
+      return;
     checkMissingMemberInitializer(*Result.Context, *Ctor->getParent(), Ctor);
     checkMissingBaseClassInitializer(*Result.Context, *Ctor->getParent(), Ctor);
   } else if (const auto *Record =
Index: clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines-pro-type-member-init.cpp
===================================================================
--- clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines-pro-type-member-init.cpp
+++ clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines-pro-type-member-init.cpp
@@ -501,3 +501,19 @@
 void Bug33557() {
   NegativeImplicitInheritedCtor I(5);
 }
+
+struct NegativeDefaultedCtorOutOfDecl {
+  NegativeDefaultedCtorOutOfDecl(const NegativeDefaultedCtorOutOfDecl &);
+  int F;
+};
+
+NegativeDefaultedCtorOutOfDecl::NegativeDefaultedCtorOutOfDecl(const NegativeDefaultedCtorOutOfDecl &) = default;
+
+struct PositiveDefaultConstructorOutOfDecl {
+  PositiveDefaultConstructorOutOfDecl();
+  int F;
+  // CHECK-FIXES: int F{};
+};
+
+PositiveDefaultConstructorOutOfDecl::PositiveDefaultConstructorOutOfDecl() = default;
+// CHECK-MESSAGES: :[[@LINE-1]]:1: warning: constructor does not initialize these fields: F