diff --git a/lib/isc/jemalloc_shim.h b/lib/isc/jemalloc_shim.h
index 8d99c7b776..37e984ae1a 100644
--- a/lib/isc/jemalloc_shim.h
+++ b/lib/isc/jemalloc_shim.h
@@ -64,7 +64,15 @@ sallocx(void *ptr, int flags) {
 
 #elif HAVE_MALLOC_USABLE_SIZE
 
+#ifdef __DragonFly__
+/*
+ * On DragonFly BSD 'man 3 malloc' advises us to include the following
+ * header to have access to malloc_usable_size().
+ */
+#include <malloc_np.h>
+#else
 #include <malloc.h>
+#endif
 
 static inline size_t
 sallocx(void *ptr, int flags) {
diff --git a/lib/isc/mem.c b/lib/isc/mem.c
index 61b7222491..df75f6eab6 100644
--- a/lib/isc/mem.c
+++ b/lib/isc/mem.c
@@ -44,7 +44,8 @@
 #include <json_object.h>
 #endif /* HAVE_JSON_C */
 
-#if defined(HAVE_MALLOC_NP_H)
+/* On DragonFly BSD the header does not provide jemalloc API */
+#if defined(HAVE_MALLOC_NP_H) && !defined(__DragonFly__)
 #include <malloc_np.h>
 #elif defined(HAVE_JEMALLOC)
 #include <jemalloc/jemalloc.h>