diff --git a/spec/support/extension_helper.rb b/spec/support/extension_helper.rb
index 35b22f9..9baca78 100644
--- a/spec/support/extension_helper.rb
+++ b/spec/support/extension_helper.rb
@@ -5,7 +5,7 @@ def install_testing_extension
         mkdir -p #{spec_root}/dumbo_sample_runtime && \
         cp -a #{spec_root}/dumbo_sample/* #{spec_root}/dumbo_sample_runtime
         cd #{spec_root}/dumbo_sample_runtime && \
-        ls /usr/lib/postgresql/9.5/ && \
+        ls /usr/lib/postgresql/9.5/bin && \
         echo `pg_config` && \
         make && make install
       )