diff --git a/src/base/func_util.hh b/src/base/func_util.hh
index 6c461c32..760deb4d 100644
--- a/src/base/func_util.hh
+++ b/src/base/func_util.hh
@@ -90,13 +90,19 @@ invoke(Fn&& f, Args&&... args) noexcept(
 
 template<class F, class... Args>
 struct is_invocable {
-    template<class U>
-    static auto test(U* p)
-        -> decltype((*p)(std::declval<Args>()...), void(), std::true_type());
-    template<class U>
+    template<typename U, typename Obj, typename... FuncArgs>
+    static auto test(U&& p)
+        -> decltype((std::declval<Obj>().*p)(std::declval<FuncArgs>()...),
+                    void(),
+                    std::true_type());
+    template<typename U, typename... FuncArgs>
+    static auto test(U* p) -> decltype((*p)(std::declval<FuncArgs>()...),
+                                       void(),
+                                       std::true_type());
+    template<typename U, typename... FuncArgs>
     static auto test(...) -> decltype(std::false_type());
 
-    static constexpr bool value = decltype(test<F>(0))::value;
+    static constexpr bool value = decltype(test<F, Args...>(0))::value;
 };
 
 }  // namespace func
diff --git a/src/base/itertools.hh b/src/base/itertools.hh
index e11c2309..d0e5b5fc 100644
--- a/src/base/itertools.hh
+++ b/src/base/itertools.hh
@@ -533,10 +533,11 @@ operator|(nonstd::optional<T> in,
 template<typename T, typename F>
 auto
 operator|(const T& in, const lnav::itertools::details::mapper<F>& mapper)
-    -> std::vector<decltype(mapper.m_func(typename T::value_type{}))>
+    -> std::vector<
+        decltype(mapper.m_func(std::declval<typename T::value_type>()))>
 {
-    using return_type
-        = std::vector<decltype(mapper.m_func(typename T::value_type{}))>;
+    using return_type = std::vector<decltype(mapper.m_func(
+        std::declval<typename T::value_type>()))>;
     return_type retval;
 
     retval.reserve(in.size());
@@ -605,7 +606,9 @@ operator|(const std::vector<std::shared_ptr<T>>& in,
     return retval;
 }
 
-template<typename T, typename F>
+template<typename T,
+         typename F,
+         std::enable_if_t<!lnav::func::is_invocable<F, T>::value, int> = 0>
 auto
 operator|(const std::vector<T>& in,
           const lnav::itertools::details::mapper<F>& mapper)