diff --git a/doc/mimalloc-doc.h b/doc/mimalloc-doc.h
index 69367e66..3d2a1985 100644
--- a/doc/mimalloc-doc.h
+++ b/doc/mimalloc-doc.h
@@ -680,7 +680,7 @@ free lists, etc, as:
 ```
 > mkdir -p out/secure
 > cd out/secure
-> cmake -DSECURE=ON ../..
+> cmake -DMI_SECURE=ON ../..
 > make
 ```
 This will name the shared library as `libmimalloc-secure.so`.
diff --git a/readme.md b/readme.md
index 4bf990c7..a1bd4021 100644
--- a/readme.md
+++ b/readme.md
@@ -93,7 +93,7 @@ free lists, etc, as:
 ```
 > mkdir -p out/secure
 > cd out/secure
-> cmake -DSECURE=ON ../..
+> cmake -DMI_SECURE=ON ../..
 > make
 ```
 This will name the shared library as `libmimalloc-secure.so`.