diff --git a/php/tests/compile_extension.sh b/php/tests/compile_extension.sh
index d6dcabcbbb..daa6b17809 100755
--- a/php/tests/compile_extension.sh
+++ b/php/tests/compile_extension.sh
@@ -10,7 +10,7 @@ rm -f configure.in configure.ac
 php make-preload.php
 phpize
 if [ "$1" = "--release" ]; then
-  ./configure --with-php-config=$(which php-config)
+  ./configure --with-php-config=$(which php-config) CFLAGS="-DNDEBUG"
 else
   # To get debugging symbols in PHP itself, build PHP with:
   #   $ ./configure --enable-debug CFLAGS='-g -O0'