diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 62812f90a..3a9b7a3c0 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -875,7 +875,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
         if (hasOverrides) {
             Value * vOverrides = (*v.attrs)[overrides->second.displ].value;
             state.forceAttrs(*vOverrides);
-            Bindings * newBnds = state.allocBindings(v.attrs->size() + vOverrides->attrs->size());
+            Bindings * newBnds = state.allocBindings(v.attrs->capacity() + vOverrides->attrs->size());
             for (auto & i : *v.attrs)
                 newBnds->push_back(i);
             for (auto & i : *vOverrides->attrs) {
diff --git a/tests/lang/eval-okay-attrs6.exp b/tests/lang/eval-okay-attrs6.exp
new file mode 100644
index 000000000..b46938032
--- /dev/null
+++ b/tests/lang/eval-okay-attrs6.exp
@@ -0,0 +1 @@
+{ __overrides = { bar = "qux"; }; bar = "qux"; foo = "bar"; }
diff --git a/tests/lang/eval-okay-attrs6.nix b/tests/lang/eval-okay-attrs6.nix
new file mode 100644
index 000000000..2e5c85483
--- /dev/null
+++ b/tests/lang/eval-okay-attrs6.nix
@@ -0,0 +1,4 @@
+rec {
+  "${"foo"}" = "bar";
+   __overrides = { bar = "qux"; };
+}