fixes #944 cmake command error for windows version
diff --git a/README.md b/README.md
index 2c692f1..3b271f0 100644
--- a/README.md
+++ b/README.md
@@ -72,7 +72,7 @@
 2.  `cd build`
 3.  `cmake ..`
 4.  `cmake --build . --config Debug`
-5.  `ctest --config Debug .`
+5.  `ctest -C Debug .`
 6.  `cmake --build . --config Debug --target install`
     *NB:* This may have to be done using an Administrator account.