diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index 5b8fdde5796..ad52c8e5a7c 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -779,7 +779,7 @@ substituteAllInPlace() {
 # the environment used for building.
 dumpVars() {
     if [ "${noDumpEnvVars:-0}" != 1 ]; then
-        export > "$NIX_BUILD_TOP/env-vars" || true
+        export >| "$NIX_BUILD_TOP/env-vars" || true
     fi
 }