diff --git a/cmake/32-bit-toolchain.cmake b/cmake/32-bit-toolchain.cmake
index fe9aa483f..253523e66 100644
--- a/cmake/32-bit-toolchain.cmake
+++ b/cmake/32-bit-toolchain.cmake
@@ -26,7 +26,9 @@
 # STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 # THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-set (CMAKE_SYSTEM_NAME Windows)
+if (NOT CMAKE_HOST_WIN32)
+  set (CMAKE_SYSTEM_NAME Windows)
+endif()
 
 set (GCC_PREFIX i686-w64-mingw32)
 set (CMAKE_C_COMPILER ${GCC_PREFIX}-gcc)
diff --git a/cmake/64-bit-toolchain.cmake b/cmake/64-bit-toolchain.cmake
index 20b568c71..b4b528347 100644
--- a/cmake/64-bit-toolchain.cmake
+++ b/cmake/64-bit-toolchain.cmake
@@ -26,7 +26,9 @@
 # STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 # THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-set (CMAKE_SYSTEM_NAME Windows)
+if (NOT CMAKE_HOST_WIN32)
+  set (CMAKE_SYSTEM_NAME Windows)
+endif()
 
 set (GCC_PREFIX x86_64-w64-mingw32)
 set (CMAKE_C_COMPILER ${GCC_PREFIX}-gcc)