diff --git a/lld/MachO/Writer.cpp b/lld/MachO/Writer.cpp
--- a/lld/MachO/Writer.cpp
+++ b/lld/MachO/Writer.cpp
@@ -372,10 +372,14 @@
     }
   }
 
-  // TODO: dyld requires libSystem to be loaded. libSystem is a universal
-  // binary and we don't have support for that yet, so mock it out here.
-  headerSection->addLoadCommand(
-      make<LCLoadDylib>("/usr/lib/libSystem.B.dylib"));
+  // dyld requires us to load libSystem. This environment variable is used in
+  // tests, as we may also run those tests on non-OSX systems which do not
+  // have libSystem.
+  if (StringRef(getenv("LLD_IN_TEST")) == "1" && dylibOrdinal == 1 &&
+      config->outputType == MH_EXECUTE) {
+    headerSection->addLoadCommand(
+        make<LCLoadDylib>("/usr/lib/libSystem.B.dylib"));
+  }
 }
 
 void Writer::createHiddenSections() {