diff --git a/.github/workflows/quick.yaml b/.github/workflows/quick.yaml
index 2383244752a..60230415163 100644
--- a/.github/workflows/quick.yaml
+++ b/.github/workflows/quick.yaml
@@ -136,7 +136,7 @@ jobs:
           sudo sed --in-place -E 's/# (deb-src.*updates main)/  \1/g' /etc/apt/sources.list
           sudo apt-get --quiet=2 update
           sudo apt-get --quiet=2 build-dep squid
-          sudo apt-get --quiet=2 install linuxdoc-tools libtool-bin ${{ matrix.compiler.CC }} ccache
+          sudo apt-get --quiet=2 install linuxdoc-tools libtool-bin ${{ matrix.compiler.CC }} ccache valgrind
 
       - name: Checkout sources
         uses: actions/checkout@v4
diff --git a/test-suite/buildtest.sh b/test-suite/buildtest.sh
index 0c3ab21b56d..41a51741eae 100755
--- a/test-suite/buildtest.sh
+++ b/test-suite/buildtest.sh
@@ -16,6 +16,22 @@
 action="${1}"
 config="${2}"
 
+# Allow a layer to enable optional default-disabled features when
+# those features are supported in the current build environment
+# (and we can easily detect such support).
+if ${PKG_CONFIG:-pkg-config} --exists 'libecap >= 1.0 libecap < 1.1' 2>/dev/null
+then
+    CONFIGURE_FLAGS_MAYBE_ENABLE_ECAP="--enable-ecap"
+else
+    echo "WARNING: eCAP testing disabled" >&2
+fi
+if ${PKG_CONFIG:-pkg-config} --exists valgrind 2>/dev/null
+then
+    CONFIGURE_FLAGS_MAYBE_ENABLE_VALGRIND="--with-valgrind-debug"
+else
+    echo "WARNING: Valgrind testing disabled" >&2
+fi
+
 # cache_file may be set by environment variable
 configcache=""
 if [ -n "$cache_file" ]; then
diff --git a/test-suite/buildtests/layer-02-maximus.opts b/test-suite/buildtests/layer-02-maximus.opts
index ce03ab5350b..b8fc383b637 100644
--- a/test-suite/buildtests/layer-02-maximus.opts
+++ b/test-suite/buildtests/layer-02-maximus.opts
@@ -37,11 +37,9 @@ MAKETEST="distcheck"
 #	We can't test them automatically everywhere without detecting those
 #	optional packages first.
 #
-#   --enable-ecap \
 #   --enable-epoll \
 #   --enable-kqueue \
 #   --enable-win32-service \
-#   --with-valgrind-debug \
 #   --with-gnutls \
 #   --with-tdb \
 #   --with-cap \
@@ -110,6 +108,8 @@ DISTCHECK_CONFIGURE_FLAGS=" \
 	--enable-build-info=squid\ test\ build \
 	--enable-ssl-crtd \
 	--with-openssl \
+	$CONFIGURE_FLAGS_MAYBE_ENABLE_ECAP \
+	$CONFIGURE_FLAGS_MAYBE_ENABLE_VALGRIND \
 	"
 
 # Fix the distclean testing.
diff --git a/test-suite/buildtests/layer-04-noauth-everything.opts b/test-suite/buildtests/layer-04-noauth-everything.opts
index f89911b3862..4f9ecc77e7d 100644
--- a/test-suite/buildtests/layer-04-noauth-everything.opts
+++ b/test-suite/buildtests/layer-04-noauth-everything.opts
@@ -42,11 +42,9 @@ MAKETEST="distcheck"
 #	We can't test them automatically everywhere without detecting those
 #	optional packages first.
 #
-#   --enable-ecap \
 #   --enable-epoll \
 #   --enable-kqueue \
 #   --enable-win32-service \
-#   --with-valgrind-debug \
 #   --with-ldap \
 #
 #   --enable-cpu-profiling \  Requires CPU support.
@@ -110,6 +108,8 @@ DISTCHECK_CONFIGURE_FLAGS=" \
 	--with-pic \
 	--with-pthreads \
 	--enable-build-info=squid\ test\ build \
+	$CONFIGURE_FLAGS_MAYBE_ENABLE_ECAP \
+	$CONFIGURE_FLAGS_MAYBE_ENABLE_VALGRIND \
 	"
 
 # Fix the distclean testing.