diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 944c7b1af..bde721401 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -359,11 +359,18 @@ string_parts_interpolated
 
 path_start
   : PATH {
-    Path path(absPath(std::string_view{$1.p, $1.l}, state->basePath.path.abs()));
+    std::string_view literal({$1.p, $1.l});
+    Path path(absPath(literal, state->basePath.path.abs()));
     /* add back in the trailing '/' to the first segment */
-    if ($1.p[$1.l-1] == '/' && $1.l > 1)
-      path += "/";
-    $$ = new ExprPath(ref<SourceAccessor>(state->rootFS), std::move(path));
+    if (literal.size() > 1 && literal.back() == '/')
+      path += '/';
+    $$ =
+        /* Absolute paths are always interpreted relative to the
+           root filesystem accessor, rather than the accessor of the
+           current Nix expression. */
+        literal.front() == '/'
+        ? new ExprPath(state->rootFS, std::move(path))
+        : new ExprPath(state->basePath.accessor, std::move(path));
   }
   | HPATH {
     if (state->settings.pureEval) {