diff --git a/util/net/http_transport_win.cc b/util/net/http_transport_win.cc
index 9698df30..dc3eeeb7 100644
--- a/util/net/http_transport_win.cc
+++ b/util/net/http_transport_win.cc
@@ -101,6 +101,12 @@ std::string WinHttpMessage(const char* extra) {
                               GetLastError(),
                               error_code);
   }
+
+  // Most system messages end in a space. Remove the space if it’s there,
+  // because the StringPrintf() below includes one.
+  if (len >= 1 && msgbuf[len - 1] == ' ') {
+    msgbuf[len - 1] = '\0';
+  }
   return base::StringPrintf("%s: %s (0x%lx)", extra, msgbuf, error_code);
 }