diff --git a/usr/share/genmkfile/make-helper-one.bsh b/usr/share/genmkfile/make-helper-one.bsh
index c8e0179..a1469c1 100755
--- a/usr/share/genmkfile/make-helper-one.bsh
+++ b/usr/share/genmkfile/make-helper-one.bsh
@@ -1147,6 +1147,9 @@ beforehand?
          sudo \
             $COWBUILDER_PREFIX \
                env \
+                  --unset=TEMP \
+                  --unset=TEMPDIR \
+                  --unset=TMP \
                   --unset=TMPDIR \
                      cowbuilder \
                         --debbuildopts="-sa" \