diff --git a/config.nims b/config.nims
index cd9029f21..89cea8017 100644
--- a/config.nims
+++ b/config.nims
@@ -38,6 +38,8 @@ else:
 # enable metric collection
 --define:metrics
 --define:chronicles_line_numbers
+# for heap-usage-by-instance-type metrics and object base-type strings
+--define:nimTypeNames
 
 # the default open files limit is too low on macOS (512), breaking the
 # "--debugger:native" build. It can be increased with `ulimit -n 1024`.