diff --git a/INSTALL.md b/INSTALL.md
index a97b610..7fc6696 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -32,7 +32,7 @@ Requirements
   | GNU Readline | 6.0             |
   | [Tcl]        | 8.6             |
   | [uriparser]  | 0.9             |
-  | xxHash       | 8.8             |
+  | xxHash       | 0.8             |
 
   Some of them can be optional, depending on which components of BookmarkFS
   are to be built, and which features are enabled.
@@ -44,13 +44,16 @@ Requirements
     * Automake
     * Libtool
     * Autoconf Archive
-  - pkg-config
-  - POSIX-compatible make
-  - C99-capable C compiler (GCC or Clang is recommended)
+  - `pkg-config`
+  - POSIX-compatible `make`
+    * One with `VPATH` support is recommended
+  - C99-capable C compiler
+    * GCC or Clang is recommended
 
   Optionally:
 
-  - GNU Texinfo, for building the user manual
+  - GNU Texinfo
+    * For building the user manual
 
 
 Installation
@@ -96,7 +99,7 @@ Installation
   - `--disable-sandbox`
     * Build the utility library without sandboxing features
     * No longer requires: libseccomp
-  - `--disable-landlock` (Linux-only)
+  - `--disable-sandbox-landlock` (Linux-only)
     * Disable the [Landlock] feature in the sandbox implementation
   - `--enable-xxhash-inline`
     * Use xxHash as a header-only library
diff --git a/configure.ac b/configure.ac
index 1d5a09d..ef29e10 100644
--- a/configure.ac
+++ b/configure.ac
@@ -77,9 +77,13 @@ BOOKMARKFS_FEAT([sandbox], [yes], [sandboxing], [
             [Define to 1 if sandboxing is enabled.])
 ])
 
-BOOKMARKFS_FEAT([landlock], [yes], [Linux Landlock features for sandboxing], [
-    AC_DEFINE([BOOKMARKFS_SANDBOX_LANDLOCK], [1],
-            [Define to 1 if Linux Landlock is enabled.])
+AS_VAR_IF([host_os_is_linux], [yes], [
+    BOOKMARKFS_FEAT([sandbox-landlock], [yes],
+            [Linux Landlock features for sandboxing],
+    [
+        AC_DEFINE([BOOKMARKFS_SANDBOX_LANDLOCK], [1],
+                [Define to 1 if Landlock is enabled for sandboxing.])
+    ])
 ])
 
 BOOKMARKFS_FEAT([xxhash-inline], [no],
diff --git a/m4/bookmarkfs_ac.m4 b/m4/bookmarkfs_ac.m4
index 02045f0..f658d4d 100644
--- a/m4/bookmarkfs_ac.m4
+++ b/m4/bookmarkfs_ac.m4
@@ -64,13 +64,13 @@ AC_DEFUN([BOOKMARKFS_DEP], [
             ])
         ])
     ], [
-        AS_VAR_SET([SAVED_PKG_CONFIG_PATH_], ["${PKG_CONFIG_PATH}"])
+        AS_VAR_SET([old_pkg_config_path_], ["${PKG_CONFIG_PATH}"])
         AS_VAR_IF([with_var_], [yes], , [
-            AS_VAR_SET([PKG_CONFIG_PATH], ["${with_$1}:${PKG_CONFIG_PATH}"])
+            AS_VAR_SET([PKG_CONFIG_PATH], ["${with_var_}:${PKG_CONFIG_PATH}"])
+            export PKG_CONFIG_PATH
         ])
-        export PKG_CONFIG_PATH
         PKG_CHECK_MODULES(m4_toupper([$1]), [$1 $2], [$4])
-        AS_VAR_SET([PKG_CONFIG_PATH], ["${SAVED_PKG_CONFIG_PATH_}"])
+        AS_VAR_SET([PKG_CONFIG_PATH], ["${old_pkg_config_path_}"])
     ])
     m4_popdef([with_var_])
 ])