diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index ba583d46cf93200cc70f7016b669e4e905c1714c..8ee796be70c59282c4ecc27693733f0063d5b552 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -260,6 +260,7 @@ include:
 .check_nag:
   variables:
     FC: nagfor
+    FCFLAGS: -g -O2 -C=all
     # Ignore Questionable warnings:
     WARNINGS_AWK_SCRIPT: '!/^\[NAG Fortran Compiler normal termination/ && (/warning/ || /WARNING/ || /Warning/)'
   before_script: