diff --git a/.dockers/ubuntu-20/user-config.jam b/.dockers/ubuntu-20/user-config.jam
index 87ee4173..71872703 100644
--- a/.dockers/ubuntu-20/user-config.jam
+++ b/.dockers/ubuntu-20/user-config.jam
@@ -7,5 +7,5 @@ feature.compose <asio.mode>ts : <define>"BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT"
 feature.compose <asio.mode>nodep-nots : <define>"BOOST_ASIO_NO_DEPRECATED" <define>"BOOST_ASIO_NO_TS_EXECUTORS" ;
 feature.compose <asio.mode>nodep-ts : <define>"BOOST_ASIO_NO_DEPRECATED" <define>"BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT" ;
 
-using clang :   : clang++ : <cxxflags>-stdlib=libc++ <cxxflags>"-DBOOST_ASIO_DISABLE_CONCEPTS" <cxxflags>"-Wno-c99-extensions" <linkflags>-stdlib=libc++ ;
+using clang :   : clang++ : <cxxflags>-stdlib=libc++ <cxxflags>"-Wno-c99-extensions" <linkflags>-stdlib=libc++ ;
 using gcc :   : g++ : <cxxflags>"-Wno-c99-extensions" ;
diff --git a/.dockers/ubuntu-focal/Dockerfile b/.dockers/ubuntu-focal/Dockerfile
new file mode 100644
index 00000000..6535e4c9
--- /dev/null
+++ b/.dockers/ubuntu-focal/Dockerfile
@@ -0,0 +1,19 @@
+FROM ubuntu:focal
+
+RUN apt-get update
+RUN DEBIAN_FRONTEND="noninteractive" apt-get -y install tzdata
+RUN apt-get install -y build-essential
+RUN apt-get install -y git cmake libssl-dev clang libc++-dev libc++abi-dev libbz2-dev zlib1g-dev
+
+WORKDIR /devel
+RUN git clone -b develop https://github.com/boostorg/boost.git
+COPY .dockers/ubuntu-focal/user-config.jam /devel/boost/
+COPY .dockers/ubuntu-focal/tests.sh /devel/boost/
+
+WORKDIR /devel/boost
+RUN git submodule update --init --recursive
+COPY . /devel/boost/libs/beast/
+
+RUN ./bootstrap.sh
+RUN ./b2 toolset=gcc variant=release cxxstd=latest headers
+RUN ./tests.sh || true
diff --git a/.dockers/ubuntu-focal/tests.sh b/.dockers/ubuntu-focal/tests.sh
new file mode 100755
index 00000000..e1706eab
--- /dev/null
+++ b/.dockers/ubuntu-focal/tests.sh
@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+
+set -e
+
+# cxxstd=2a,17,14,11 \
+
+./b2 --user-config=./user-config.jam \
+  toolset=clang,gcc \
+  asio.mode=dflt,nodep,nots,ts,nodep-nots,nodep-ts \
+  variant=release \
+  cxxstd=14,11 \
+  -j`grep processor /proc/cpuinfo | wc -l` \
+  -q \
+  libs/beast/test libs/beast/example
diff --git a/.dockers/ubuntu-focal/user-config.jam b/.dockers/ubuntu-focal/user-config.jam
new file mode 100644
index 00000000..544e0eb1
--- /dev/null
+++ b/.dockers/ubuntu-focal/user-config.jam
@@ -0,0 +1,11 @@
+import feature ;
+
+feature.feature asio.mode : dflt nodep nots ts nodep-nots nodep-ts : propagated composite ;
+feature.compose <asio.mode>nodep : <define>"BOOST_ASIO_NO_DEPRECATED" ;
+feature.compose <asio.mode>nots : <define>"BOOST_ASIO_NO_TS_EXECUTORS" ;
+feature.compose <asio.mode>ts : <define>"BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT" ;
+feature.compose <asio.mode>nodep-nots : <define>"BOOST_ASIO_NO_DEPRECATED" <define>"BOOST_ASIO_NO_TS_EXECUTORS" ;
+feature.compose <asio.mode>nodep-ts : <define>"BOOST_ASIO_NO_DEPRECATED" <define>"BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT" ;
+
+using clang :   : clang++ : <stdlib>"libc++" <cxxflags>"-Wno-c99-extensions" ;
+using gcc :   : g++ : <cxxflags>"-Wno-c99-extensions" ;
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 751ad235..2a06be02 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,4 @@
+* Fix C++20 coroutine tests.
 * Fix links to Bishop Fox Security Assessment.
 
 --------------------------------------------------------------------------------
diff --git a/test/beast/core/basic_stream.cpp b/test/beast/core/basic_stream.cpp
index 24b94d04..8fa736a6 100644
--- a/test/beast/core/basic_stream.cpp
+++ b/test/beast/core/basic_stream.cpp
@@ -1339,7 +1339,7 @@ public:
             {
                 void
                 operator()(error_code const &,
-                    net::ip::tcp::endpoint const &) const;
+                           net::ip::tcp::resolver::results_type::const_iterator) const;
             };
 
             static_assert(std::is_void<decltype(
@@ -1355,7 +1355,7 @@ public:
             {
                 void
                 operator()(error_code const &,
-                    net::ip::tcp::resolver::results_type::const_iterator);
+                           net::ip::tcp::endpoint const &);
             };
 
             static_assert(std::is_void<decltype(