diff --git a/configure.in b/configure.in
index 5419a113224..3207f2b8282 100644
--- a/configure.in
+++ b/configure.in
@@ -440,7 +440,7 @@ AC_ARG_ENABLE(debug,
 AC_MSG_CHECKING(whether to include debugging symbols)
 AC_MSG_RESULT($PHP_DEBUG)
 
-if test "$PHP_DEBUG"; then
+if test "$PHP_DEBUG" = "yes"; then
   AC_DEFINE(DEBUG,1)
   PHP_DEBUG=1
   ZEND_DEBUG=yes