diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index a3f411a5f..517952164 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -307,7 +307,7 @@ EvalState::EvalState(const Strings & _searchPath, ref<Store> store)
 
     assert(gcInitialised);
 
-    static_assert(sizeof(Env) == 16, "environment must be 16 bytes");
+    static_assert(sizeof(Env) <= 16, "environment must be <= 16 bytes");
 
     /* Initialise the Nix expression search path. */
     if (!evalSettings.pureEval) {