diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0e33d28cf..6f1bc382e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -565,6 +565,12 @@ if(WITH_MYFILE_MMAP)
     add_definitions(-DMYFILE_MMAP)
 endif()
 
+# Atomic is required in some builds: #6821
+find_package(ATOMIC)
+if(ATOMIC_FOUND)
+	target_link_libraries(executable ${ATOMIC_LIBRARIES})
+endif()
+
 if(WITH_LTO)
     # Using LTO with older versions of binutils requires setting extra flags
     set(BINUTILS_VERSION_MININUM "2.29")
diff --git a/cmake/modules/FindATOMIC.cmake b/cmake/modules/FindATOMIC.cmake
new file mode 100644
index 000000000..1669983c3
--- /dev/null
+++ b/cmake/modules/FindATOMIC.cmake
@@ -0,0 +1,36 @@
+include(CheckCXXSourceCompiles)
+
+set(ATOMIC_CXX_TEST_SOURCE
+"
+#include <atomic>
+int main() {
+	std::atomic<bool> b(false);
+	std::atomic<int> i(0);
+	std::atomic<unsigned int> ui(0);
+	b.exchange(true);
+	++i;
+	return ++ui;
+}
+")
+
+set(SAFE_CMAKE_REQUIRED_LIBRARIES "${CMAKE_REQUIRED_LIBRARIES}")
+list(REMOVE_ITEM CMAKE_REQUIRED_LIBRARIES "atomic")
+
+check_cxx_source_compiles("${ATOMIC_CXX_TEST_SOURCE}" HAVE_CXX_ATOMICS_WITHOUT_LIB)
+
+if(NOT HAVE_CXX_ATOMICS_WITHOUT_LIB)
+	list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
+	check_cxx_source_compiles("${ATOMIC_CXX_TEST_SOURCE}" HAVE_CXX_ATOMICS_WITH_LIB)
+	if (NOT HAVE_CXX_ATOMICS_WITH_LIB)
+		message(FATAL_ERROR "libatomic support needed for std::atomic<> but not 
+found.")
+	endif()
+	set(ATOMIC_LIBRARIES "atomic")
+	set(ATOMIC_FOUND ON)
+endif()
+
+set(CMAKE_REQUIRED_LIBRARIES "${SAFE_CMAKE_REQUIRED_LIBRARIES}")
+unset(SAFE_CMAKE_REQUIRED_LIBRARIES)
+
+mark_as_advanced(ATOMIC_LIBRARIES)
+mark_as_advanced(ATOMIC_FOUND)
diff --git a/rtgui/CMakeLists.txt b/rtgui/CMakeLists.txt
index fb4acbe42..592b816a0 100644
--- a/rtgui/CMakeLists.txt
+++ b/rtgui/CMakeLists.txt
@@ -251,9 +251,10 @@ else()
 endif()
 
 # Excluding libatomic needed by Clang/FreeBSD, #3636
-if(OPENMP_FOUND AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD")
-    set(EXTRA_LIB_RTGUI "${EXTRA_LIB_RTGUI}" "atomic")
-endif()
+# Now handled in cmake/modules/findATOMIC.cmake, #6821
+# if(OPENMP_FOUND AND NOT APPLE AND NOT ${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD")
+#     set(EXTRA_LIB_RTGUI "${EXTRA_LIB_RTGUI}" "atomic")
+# endif()
 
 # Create config.h which defines where data are stored
 configure_file("${CMAKE_CURRENT_SOURCE_DIR}/config.h.in" "${CMAKE_CURRENT_BINARY_DIR}/config.h")