diff --git a/include/beman/execution/detail/run_loop.hpp b/include/beman/execution/detail/run_loop.hpp
index 50777110..06a9eab7 100644
--- a/include/beman/execution/detail/run_loop.hpp
+++ b/include/beman/execution/detail/run_loop.hpp
@@ -31,6 +31,7 @@ import beman.execution.detail.set_value;
 import beman.execution.detail.unstoppable_token;
 #else
 #include <beman/execution/detail/completion_signatures.hpp>
+#include <beman/execution/detail/env.hpp>
 #include <beman/execution/detail/get_completion_scheduler.hpp>
 #include <beman/execution/detail/get_env.hpp>
 #include <beman/execution/detail/get_forward_progress_guarantee.hpp>
@@ -90,10 +91,20 @@ class run_loop {
     };
     struct sender {
         using sender_concept = ::beman::execution::sender_tag;
-        template <typename, typename... Env>
+        template <typename Self, typename... Env>
         static consteval auto get_completion_signatures() noexcept {
-            if constexpr (::beman::execution::unstoppable_token<decltype(::beman::execution::get_stop_token(
-                              std::declval<Env>()...))>)
+            // [exec.getcomplsigs] permits sizeof...(Env) == 0. Answering that
+            // query as if for env<> matches [exec.run.loop]'s formula, whose
+            // E = env<> has an unstoppable stop token, and matches how the
+            // other environment-sensitive senders here (then, into_variant)
+            // handle the empty pack. Without this the member's body is
+            // ill-formed for an empty pack -- get_stop_token() with no
+            // argument -- and because the return type is deduced, that is a
+            // hard error rather than a substitution failure.
+            if constexpr (0u == sizeof...(Env))
+                return get_completion_signatures<Self, ::beman::execution::env<>>();
+            else if constexpr (::beman::execution::unstoppable_token<decltype(::beman::execution::get_stop_token(
+                                   std::declval<Env>()...))>)
                 return ::beman::execution::completion_signatures<::beman::execution::set_value_t()>{};
             else
                 return ::beman::execution::completion_signatures<::beman::execution::set_value_t(),
diff --git a/tests/beman/execution/exec-run-loop-types.test.cpp b/tests/beman/execution/exec-run-loop-types.test.cpp
index 4d6f43f8..cced0e8e 100644
--- a/tests/beman/execution/exec-run-loop-types.test.cpp
+++ b/tests/beman/execution/exec-run-loop-types.test.cpp
@@ -16,6 +16,7 @@ import beman.execution;
 #include <beman/execution/detail/inplace_stop_source.hpp>
 #include <beman/execution/detail/completion_signatures.hpp>
 #include <beman/execution/detail/connect.hpp>
+#include <beman/execution/detail/dependent_sender.hpp>
 #include <beman/execution/detail/start.hpp>
 #include <beman/execution/detail/get_completion_signatures.hpp>
 #include <beman/execution/detail/get_env.hpp>
@@ -98,6 +99,16 @@ TEST(exec_run_loop_types) {
         ::std::same_as<test_std::completion_signatures<test_std::set_value_t(), test_std::set_stopped_t()>,
                        decltype(test_std::get_completion_signatures<decltype(sender),
                                                                     decltype(token_env{source.get_token()})>())>);
+    // [exec.getcomplsigs] constrains sizeof...(Env) <= 1, so the
+    // zero-environment query is well-formed and must be answered. It is
+    // answered as for env<>, whose stop token is unstoppable.
+    static_assert(::std::same_as<test_std::completion_signatures<test_std::set_value_t()>,
+                                 decltype(test_std::get_completion_signatures<decltype(sender)>())>);
+    // ... and because detail::non_dependent_sender is itself spelled with that
+    // query inside a requires-expression, a sender that cannot answer it makes
+    // the concept ill-formed rather than false. Asserting the concept is what
+    // pins that down.
+    static_assert(not test_std::dependent_sender<decltype(sender)>);
     // p7:
     static_assert(
         test_std::receiver_of<receiver, decltype(test_std::get_completion_signatures<decltype(sender), env>())>);