diff --git a/similar/main/menu.cpp b/similar/main/menu.cpp
index c372b32e3..0be35063e 100644
--- a/similar/main/menu.cpp
+++ b/similar/main/menu.cpp
@@ -2332,21 +2332,32 @@ window_event_result browser::callback_handler(const d_event &event, window_event
 				return get_absolute_path(userdata, "");
 			else
 			{
-				const size_t len_newpath = strlen(newpath.data());
-				const size_t len_item = strlen(list[citem]);
-				/* The separator may or may not be included, depending on
-				 * whether one is already present.  Regardless of whether a new
-				 * separator is printed by the block, require sufficient space
-				 * for it to fit.  This is pessimistic, but should discourage
-				 * gcc's -Wformat-truncation from warning about insufficient
-				 * buffer capacity.  In practice, users should never have a
-				 * path that approaches this limit, so the `if` test should
-				 * succeed in all reasonable cases.
+				const std::size_t len_newpath{strlen(newpath.data())};
+				const std::size_t len_item{1 + strlen(list[citem])};	// also copy the trailing null
+				const std::size_t len_sep{strlen(sep)};
+				/* If `newpath` is long enough to contain a separator, test
+				 * whether it ends with a separator.  If it is not long enough
+				 * to contain one, or is tested and does not end with one, then
+				 * set `len_copy_sep` to copy from `sep`.  Otherwise, set
+				 * `len_copy_sep` to copy nothing.
 				 */
-				const size_t len_sep = strlen(sep);
-				if (len_newpath + len_item + len_sep < newpath.size())
+				const std::size_t len_copy_sep{
+					(len_newpath >= len_sep && !memcmp(&newpath[len_newpath - len_sep], sep, len_sep))
+						? std::size_t{0}
+						: len_sep
+				};
+				const std::size_t capacity_newpath{newpath.size()};
+				/* In practice, users should never have a path that approaches
+				 * this limit, so the `if` test should succeed in all
+				 * reasonable cases.
+				 */
+				if (const std::size_t total_used_after_insertion{len_newpath + len_copy_sep + len_item}; total_used_after_insertion < capacity_newpath)
 				{
-					snprintf(&newpath[len_newpath], newpath.size() - len_newpath, "%s%s", (len_newpath >= len_sep && strncmp(&newpath[len_newpath - len_sep], sep, len_sep)) ? sep : "", list[citem]);
+					const auto begin_insert_sep{std::next(newpath.begin(), len_newpath)};
+					const auto begin_insert_item{std::ranges::copy_n(sep, len_copy_sep, begin_insert_sep).out};
+					const auto end_insert_item{std::ranges::copy_n(list[citem], len_item, begin_insert_item).out};
+					(void)end_insert_item;
+					assert(end_insert_item == std::next(newpath.begin(), total_used_after_insertion));
 				}
 			}
 			if ((citem == 0) || PHYSFS_isDirectory(list[citem]))