diff --git a/build-aux/ci/build-osx.sh b/build-aux/ci/build-osx.sh
index 8e7abcc..48dc27b 100755
--- a/build-aux/ci/build-osx.sh
+++ b/build-aux/ci/build-osx.sh
@@ -1,5 +1,8 @@
 #!/usr/bin/env bash
-set -ex
+set -e
+
+# Avoid weird interleaving due to buffering.
+exec 1>&2
 
 # Link to the same OpenSSL version as libfido2.
 OPENSSL="$(brew deps libfido2 | grep openssl)"
@@ -9,5 +12,72 @@ export PKG_CONFIG_PATH="${LIBFIDO2_PKGCONF}:${OPENSSL_PKGCONF}"
 
 ./autogen.sh
 ./configure --disable-silent-rules --disable-man
-make -j $(sysctl -n hw.logicalcpu)
+make -j "$(sysctl -n hw.logicalcpu)"
 make check
+
+d_PREFIX="$PWD/my_p"
+d_PREFIX_ALT="$PWD/my_p_ALT"
+d_DEST="$PWD/my_d"
+
+reset() {
+  mkdir -p "$d_PREFIX" && rm -rf "${d_PREFIX:?}/"*
+  mkdir -p "$d_PREFIX_ALT" && rm -rf "${d_PREFIX_ALT:?}/"*
+  mkdir -p "$d_DEST" && rm -rf "${d_DEST:?}/"*
+}
+
+view() {
+  : VIEW PREFIX
+  ls -lR "$d_PREFIX"
+
+  : VIEW PREFIX_ALT
+  ls -lR "$d_PREFIX_ALT"
+
+  : VIEW DESTDIR
+  ls -lR "$d_DEST"
+}
+
+reset
+
+set -x
+
+: XXX 000
+./configure --disable-silent-rules --disable-man
+make install || :
+view
+reset
+
+: XXX 001
+make install DESTDIR="$d_DEST" || :
+view
+reset
+
+: XXX 010
+make install prefix="$d_PREFIX" || :
+view
+reset
+
+: XXX 011
+make install prefix="$d_PREFIX" DESTDIR="$d_DEST" || :
+view
+reset
+
+: XXX 100
+./configure --disable-silent-rules --disable-man --prefix="$d_PREFIX"
+make install || :
+view
+reset
+
+: XXX 101
+make install DESTDIR="$d_DEST" || :
+view
+reset
+
+: XXX 110
+make install prefix="$d_PREFIX" || :
+view
+reset
+
+: XXX 111
+make install prefix="$d_PREFIX" DESTDIR="$d_DEST" || :
+view
+reset