diff --git a/lib/isc/mem.c b/lib/isc/mem.c
index 2ef4e28583..70c8b6b86e 100644
--- a/lib/isc/mem.c
+++ b/lib/isc/mem.c
@@ -402,12 +402,13 @@ mem_get(isc_mem_t *ctx, size_t size, int flags) {
 }
 
 static thread_local size_t freed_bytes = 0;
-static _Atomic(isc_stdtime_t) last_purge = 0;
 
 constexpr size_t purge_threshold = (16 * 1024 * 1024);
 
 #if defined(JEMALLOC_API_SUPPORTED) || defined(__GLIBC__)
 
+static _Atomic(isc_stdtime_t) last_purge = 0;
+
 static void
 mem_purge(void) {
 	isc_stdtime_t now = isc_stdtime_now();