diff --git a/conanfile.py b/conanfile.py
index 0e8d6f16..a1b56c42 100644
--- a/conanfile.py
+++ b/conanfile.py
@@ -46,7 +46,8 @@ class UnitsConan(ConanFile):
     exports_sources = ["docs/*", "src/*", "test/*", "cmake/*", "example/*","CMakeLists.txt"]
     settings = "os", "compiler", "build_type", "arch"
     requires = (
-        "fmt/6.2.1"
+        "fmt/6.2.1",
+        "ms-gsl/3.1.0"
     )
     # scm = {
     #     "type": "git",
diff --git a/docs/usage.rst b/docs/usage.rst
index 97dd861a..2f38e3f3 100644
--- a/docs/usage.rst
+++ b/docs/usage.rst
@@ -16,7 +16,8 @@ This repository contains three independent CMake-based projects:
   - header-only project containing whole **mp-units** library
   - when C++20 support will be fully supported by C++ compilers this library will have
     no external dependencies but until then it depends on
-    `range-v3 <https://github.com/ericniebler/range-v3>`_ (only for gcc versions < 10.0)
+    `range-v3 <https://github.com/ericniebler/range-v3>`_ (only for gcc versions < 10.0),
+    `ms-gsl <https://github.com/microsoft/GSL>`_,
     and `{fmt} <https://github.com/fmtlib/fmt>`_ libraries.
 
 - *.*
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 1da2d0fa..fe22dba3 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -56,6 +56,7 @@ target_compile_features(units INTERFACE cxx_std_20)
 target_link_libraries(units
     INTERFACE
         $<IF:$<TARGET_EXISTS:CONAN_PKG::fmt>,CONAN_PKG::fmt,fmt::fmt>
+        $<IF:$<TARGET_EXISTS:CONAN_PKG::ms-gsl>,CONAN_PKG::ms-gsl,Microsoft.GSL::GSL>
 )
 target_include_directories(units
     INTERFACE
diff --git a/src/include/units/bits/ratio_maths.h b/src/include/units/bits/ratio_maths.h
index c56e95e2..79b8aa30 100644
--- a/src/include/units/bits/ratio_maths.h
+++ b/src/include/units/bits/ratio_maths.h
@@ -30,6 +30,7 @@
 #include <numeric>
 #include <tuple>
 #include <type_traits>
+#include <gsl/gsl>
 
 namespace units::detail {
 
diff --git a/src/include/units/symbol_text.h b/src/include/units/symbol_text.h
index ca9d09a0..e603b491 100644
--- a/src/include/units/symbol_text.h
+++ b/src/include/units/symbol_text.h
@@ -2,6 +2,7 @@
 
 #include <units/bits/external/fixed_string.h>
 #include <units/bits/external/hacks.h>
+#include <gsl/gsl>
 
 namespace units {
 
diff --git a/test/metabench/make_dimension/hacks.h b/test/metabench/make_dimension/hacks.h
index 31ed51bd..88b24a11 100644
--- a/test/metabench/make_dimension/hacks.h
+++ b/test/metabench/make_dimension/hacks.h
@@ -24,13 +24,6 @@
 
 #include <concepts/concepts.hpp>
 
-#ifdef NDEBUG
-#define Expects(cond) (void)(cond);
-#else
-#include <cassert>
-#define Expects(cond) assert(cond);
-#endif
-
 namespace std {
 
   // concepts