diff --git a/configure.ac b/configure.ac
index 39e8063276..10087e3b0b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -607,7 +607,11 @@ path_remove () {
 path_push_unique () {
   x="$(eval echo \$$1)"
   x="$(path_remove "$x" "$2")"
-  eval export $1="$2:$x"
+  if test -z "$x"; then
+    eval export $1="$2"
+  else
+    eval export $1="$2:$x"
+  fi
 }
 
 # tweak platform specific flags