diff --git a/.cirrus.yml b/.cirrus.yml
index 7a50417e0e..2604595b92 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -161,6 +161,7 @@ sanitizer_task:
   << : *CI_TEMPLATE
   test_fuzzers_script: ./ci/test-fuzzers.sh
   env:
+    CXXFLAGS: -DZEEK_DICT_DEBUG
     ZEEK_CI_CONFIGURE_FLAGS: *SANITIZER_CONFIG
     ZEEK_TAILORED_UB_CHECKS: 1
     UBSAN_OPTIONS: print_stacktrace=1
diff --git a/src/Dict.cc b/src/Dict.cc
index f4144fb464..06aa643ee0 100644
--- a/src/Dict.cc
+++ b/src/Dict.cc
@@ -17,7 +17,7 @@
 
 #include "3rdparty/doctest.h"
 
-#ifdef DEBUG
+#if defined(DEBUG) && defined(ZEEK_DICT_DEBUG)
 #define ASSERT_VALID(o)	o->AssertValid()
 #else
 #define ASSERT_VALID(o)