diff --git a/bin/install-site.sh b/bin/install-site.sh
index 26a5b989..f1dd2b0c 100755
--- a/bin/install-site.sh
+++ b/bin/install-site.sh
@@ -164,7 +164,7 @@ deb http://security.debian.org/ ${DISTVERSION}/updates main contrib non-free
 deb-src http://security.debian.org/ ${DISTVERSION}/updates main contrib non-free
 
 EOF
-        if [ "$BACKPORTS" == "true" ]
+        if [ x"$BACKPORTS" = x"true" ]
         then
             cat >> /etc/apt/sources.list.d/mysociety-extra.list <<EOF
 # Debian Backports
diff --git a/shlib/installfns b/shlib/installfns
index 88e7dd81..4e194e8c 100755
--- a/shlib/installfns
+++ b/shlib/installfns
@@ -164,7 +164,7 @@ deb http://security.debian.org/ ${DISTVERSION}/updates main contrib non-free
 deb-src http://security.debian.org/ ${DISTVERSION}/updates main contrib non-free
 
 EOF
-        if [ "$BACKPORTS" == "true" ]
+        if [ x"$BACKPORTS" = x"true" ]
         then
             cat >> /etc/apt/sources.list.d/mysociety-extra.list <<EOF
 # Debian Backports