diff --git a/src/libmain/include/nix/main/shared.hh b/src/libmain/include/nix/main/shared.hh
index 47d08a050..43069ba82 100644
--- a/src/libmain/include/nix/main/shared.hh
+++ b/src/libmain/include/nix/main/shared.hh
@@ -89,8 +89,6 @@ extern volatile ::sig_atomic_t blockInt;
 
 /* GC helpers. */
 
-std::string showBytes(uint64_t bytes);
-
 struct GCResults;
 
 struct PrintFreed
diff --git a/src/libmain/shared.cc b/src/libmain/shared.cc
index 4b36ec98e..3b88ea0c9 100644
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -406,7 +406,7 @@ RunPager::~RunPager()
 PrintFreed::~PrintFreed()
 {
     if (show)
-        std::cout << fmt("%d store paths deleted, %s freed\n", results.paths.size(), showBytes(results.bytesFreed));
+        std::cout << fmt("%d store paths deleted, %s freed\n", results.paths.size(), renderSize(results.bytesFreed));
 }
 
 } // namespace nix
diff --git a/src/libstore/optimise-store.cc b/src/libstore/optimise-store.cc
index 8f2878136..3e02fa812 100644
--- a/src/libstore/optimise-store.cc
+++ b/src/libstore/optimise-store.cc
@@ -312,7 +312,7 @@ void LocalStore::optimiseStore()
 
     optimiseStore(stats);
 
-    printInfo("%s freed by hard-linking %d files", showBytes(stats.bytesFreed), stats.filesLinked);
+    printInfo("%s freed by hard-linking %d files", renderSize(stats.bytesFreed), stats.filesLinked);
 }
 
 void LocalStore::optimisePath(const Path & path, RepairFlag repair)
diff --git a/src/libutil/include/nix/util/util.hh b/src/libutil/include/nix/util/util.hh
index cb1c9694d..1234937b4 100644
--- a/src/libutil/include/nix/util/util.hh
+++ b/src/libutil/include/nix/util/util.hh
@@ -333,8 +333,6 @@ struct overloaded : Ts...
 template<class... Ts>
 overloaded(Ts...) -> overloaded<Ts...>;
 
-std::string showBytes(uint64_t bytes);
-
 /**
  * Provide an addition operator between strings and string_views
  * inexplicably omitted from the standard library.
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 69826070c..f14bc63ac 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -257,9 +257,4 @@ std::pair<std::string_view, std::string_view> getLine(std::string_view s)
     }
 }
 
-std::string showBytes(uint64_t bytes)
-{
-    return fmt("%.2f MiB", bytes / (1024.0 * 1024.0));
-}
-
 } // namespace nix