diff --git a/libcxx/include/filesystem b/libcxx/include/filesystem
--- a/libcxx/include/filesystem
+++ b/libcxx/include/filesystem
@@ -1026,12 +1026,12 @@
     if (__p.has_root_directory()) {
       path __root_name_str = root_name();
       __pn_ = __root_name_str.native();
-      __pn_ += __p.__pn_.substr(__p_root_name_size);
+      __pn_ += __string_view(__p.__pn_).substr(__p_root_name_size);
       return *this;
     }
     if (has_filename() || (!has_root_directory() && is_absolute()))
       __pn_ += preferred_separator;
-    __pn_ += __p.__pn_.substr(__p_root_name_size);
+    __pn_ += __string_view(__p.__pn_).substr(__p_root_name_size);
     return *this;
   }
   template <class _Source>
diff --git a/libcxx/test/std/input.output/filesystems/class.path/path.member/path.append.pass.cpp b/libcxx/test/std/input.output/filesystems/class.path/path.member/path.append.pass.cpp
--- a/libcxx/test/std/input.output/filesystems/class.path/path.member/path.append.pass.cpp
+++ b/libcxx/test/std/input.output/filesystems/class.path/path.member/path.append.pass.cpp
@@ -175,6 +175,15 @@
     }
     assert(PathEq(LHS, E));
   }
+  {
+    path LHS(L); PathReserve(LHS, ReserveSize);
+    path RHS(R);
+    {
+      DisableAllocationGuard g;
+      LHS /= RHS;
+    }
+    assert(PathEq(LHS, E));
+  }
   // input iterator - For non-native char types, appends needs to copy the
   // iterator range into a contiguous block of memory before it can perform the
   // code_cvt conversions.