diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c06c7704308..61e7f4560fd 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -20,6 +20,9 @@ jobs:
       with:
         fetch-depth: 0
     - uses: cachix/install-nix-action@v20
+      with:
+        # The sandbox would otherwise be disabled by default on Darwin
+        extra_nix_config: "sandbox = true"
     - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
     - uses: cachix/cachix-action@v12
       if: needs.check_secrets.outputs.cachix == 'true'
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 585670e696b..71fd6e6e47e 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -2620,7 +2620,7 @@ Strings EvalSettings::getDefaultNixPath()
 {
     Strings res;
     auto add = [&](const Path & p, const std::string & s = std::string()) {
-        if (pathExists(p)) {
+        if (pathAccessible(p)) {
             if (s.empty()) {
                 res.push_back(p);
             } else {
diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index 4c66d08ee11..32e9a6ea91f 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -183,7 +183,7 @@ bool Settings::isWSL1()
 Path Settings::getDefaultSSLCertFile()
 {
     for (auto & fn : {"/etc/ssl/certs/ca-certificates.crt", "/nix/var/nix/profiles/default/etc/ssl/certs/ca-bundle.crt"})
-        if (pathExists(fn)) return fn;
+        if (pathAccessible(fn)) return fn;
     return "";
 }
 
diff --git a/src/libutil/tests/tests.cc b/src/libutil/tests/tests.cc
index 250e83a3894..f3c1e8248a0 100644
--- a/src/libutil/tests/tests.cc
+++ b/src/libutil/tests/tests.cc
@@ -202,7 +202,7 @@ namespace nix {
     }
 
     TEST(pathExists, bogusPathDoesNotExist) {
-        ASSERT_FALSE(pathExists("/home/schnitzel/darmstadt/pommes"));
+        ASSERT_FALSE(pathExists("/schnitzel/darmstadt/pommes"));
     }
 
     /* ----------------------------------------------------------------------------
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 3a8309149b2..aa0a154fd93 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -266,6 +266,17 @@ bool pathExists(const Path & path)
     return false;
 }
 
+bool pathAccessible(const Path & path)
+{
+    try {
+        return pathExists(path);
+    } catch (SysError & e) {
+        // swallow EPERM
+        if (e.errNo == EPERM) return false;
+        throw;
+    }
+}
+
 
 Path readLink(const Path & path)
 {
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index a7907cd14d7..00fcb9b7969 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -120,6 +120,14 @@ struct stat lstat(const Path & path);
  */
 bool pathExists(const Path & path);
 
+/**
+ * A version of pathExists that returns false on a permission error.
+ * Useful for inferring default paths across directories that might not
+ * be readable.
+ * @return true iff the given path can be accessed and exists
+ */
+bool pathAccessible(const Path & path);
+
 /**
  * Read the contents (target) of a symbolic link.  The result is not
  * in any way canonicalised.