diff --git a/test_common.in b/test_common.in
index 8e3c8a967..3809ef49e 100644
--- a/test_common.in
+++ b/test_common.in
@@ -1,5 +1,5 @@
 TOPSRCDIR=@abs_top_srcdir@
-TOPBUILDDIR=@abs_top_builddir@
+TOPBUILDDIR='@abs_top_builddir@'
 
 set -e