diff --git a/benchmark/cxx-source/CxxStringConversion.swift b/benchmark/cxx-source/CxxStringConversion.swift
index 6dbec589760..a10418800e2 100644
--- a/benchmark/cxx-source/CxxStringConversion.swift
+++ b/benchmark/cxx-source/CxxStringConversion.swift
@@ -15,7 +15,7 @@ import CxxStdlibPerformance
 import CxxStdlib
 
 let cxxStringSize = 1_000_000
-let swiftStringSize = 25_000
+let swiftStringSize = 1_000_000
 
 var cxxString: std.string? = nil
 var swiftString: String? = nil