diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 97147904ce..5dbbb4ad53 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -196,7 +196,7 @@ struct function_record {
     bool prepend : 1;
 
     /// Number of arguments (including py::args and/or py::kwargs, if present)
-    std::uint16_t nargs;
+    std::uint16_t nargs = 0;
 
     /// Number of trailing arguments (counted in `nargs`) that are keyword-only
     std::uint16_t nargs_kw_only = 0;
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 5578c65160..1470687867 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -104,9 +104,9 @@ struct internals {
     std::unordered_map<std::string, void *> shared_data; // Custom data to be shared across extensions
     std::vector<PyObject *> loader_patient_stack; // Used by `loader_life_support`
     std::forward_list<std::string> static_strings; // Stores the std::strings backing detail::c_str()
-    PyTypeObject *static_property_type;
-    PyTypeObject *default_metaclass;
-    PyObject *instance_base;
+    PyTypeObject *static_property_type = nullptr;
+    PyTypeObject *default_metaclass = nullptr;
+    PyObject *instance_base = nullptr;
 #if defined(WITH_THREAD)
     PYBIND11_TLS_KEY_INIT(tstate);
     PyInterpreterState *istate = nullptr;
@@ -126,9 +126,9 @@ struct internals {
 /// Additional type information which does not fit into the PyTypeObject.
 /// Changes to this struct also require bumping `PYBIND11_INTERNALS_VERSION`.
 struct type_info {
-    PyTypeObject *type;
-    const std::type_info *cpptype;
-    size_t type_size, type_align, holder_size_in_ptrs;
+    PyTypeObject *type = nullptr;
+    const std::type_info *cpptype = nullptr;
+    size_t type_size = 0, type_align = 0, holder_size_in_ptrs = 0;
     void *(*operator_new)(size_t);
     void (*init_instance)(instance *, const void *);
     void (*dealloc)(value_and_holder &v_h);
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index aee9be4e45..baa91e9562 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -65,6 +65,9 @@ struct type_caster<std::function<Return(Args...)>> {
             function f;
             func_handle(function&& f_) : f(std::move(f_)) {}
             func_handle(const func_handle& f_) {
+                operator=(f_);
+            }
+            void operator=(const func_handle &f_) & {
                 gil_scoped_acquire acq;
                 f = f_.f;
             }