diff --git a/src/libfetchers/mounted-input-accessor.cc b/src/libfetchers/mounted-input-accessor.cc
index 49917f6e5..6f397eb17 100644
--- a/src/libfetchers/mounted-input-accessor.cc
+++ b/src/libfetchers/mounted-input-accessor.cc
@@ -54,18 +54,16 @@ struct MountedInputAccessor : InputAccessor
     std::pair<ref<InputAccessor>, CanonPath> resolve(CanonPath path)
     {
         // Find the nearest parent of `path` that is a mount point.
-        std::vector<std::string> ss;
+        std::vector<std::string> subpath;
         while (true) {
             auto i = mounts.find(path);
             if (i != mounts.end()) {
-                auto subpath = CanonPath::root;
-                for (auto j = ss.rbegin(); j != ss.rend(); ++j)
-                    subpath.push(*j);
-                return {i->second, std::move(subpath)};
+                std::reverse(subpath.begin(), subpath.end());
+                return {i->second, CanonPath(subpath)};
             }
 
             assert(!path.isRoot());
-            ss.push_back(std::string(*path.baseName()));
+            subpath.push_back(std::string(*path.baseName()));
             path.pop();
         }
     }
diff --git a/src/libutil/canon-path.cc b/src/libutil/canon-path.cc
index f678fae94..1e465f1f6 100644
--- a/src/libutil/canon-path.cc
+++ b/src/libutil/canon-path.cc
@@ -13,6 +13,13 @@ CanonPath::CanonPath(std::string_view raw, const CanonPath & root)
     : path(absPath((Path) raw, root.abs()))
 { }
 
+CanonPath::CanonPath(const std::vector<std::string> & elems)
+    : path("/")
+{
+    for (auto & s : elems)
+        push(s);
+}
+
 CanonPath CanonPath::fromCwd(std::string_view path)
 {
     return CanonPath(unchecked_t(), absPath((Path) path));
diff --git a/src/libutil/canon-path.hh b/src/libutil/canon-path.hh
index eefe05ed5..6d0519f4f 100644
--- a/src/libutil/canon-path.hh
+++ b/src/libutil/canon-path.hh
@@ -6,6 +6,7 @@
 #include <cassert>
 #include <iostream>
 #include <set>
+#include <vector>
 
 namespace nix {
 
@@ -46,6 +47,11 @@ public:
         : path(std::move(path))
     { }
 
+    /**
+     * Construct a canon path from a vector of elements.
+     */
+    CanonPath(const std::vector<std::string> & elems);
+
     static CanonPath fromCwd(std::string_view path = ".");
 
     static CanonPath root;