diff --git a/include/sys/dmu.h b/include/sys/dmu.h
index 5174bdc45..d6efe2595 100644
--- a/include/sys/dmu.h
+++ b/include/sys/dmu.h
@@ -669,7 +669,8 @@ typedef struct dmu_buf_user {
 /*ARGSUSED*/
 static inline void
 dmu_buf_init_user(dmu_buf_user_t *dbu, dmu_buf_evict_func_t *evict_func_sync,
-    dmu_buf_evict_func_t *evict_func_async, dmu_buf_t **clear_on_evict_dbufp)
+    dmu_buf_evict_func_t *evict_func_async,
+    dmu_buf_t **clear_on_evict_dbufp __maybe_unused)
 {
 	ASSERT(dbu->dbu_evict_func_sync == NULL);
 	ASSERT(dbu->dbu_evict_func_async == NULL);
diff --git a/lib/libspl/include/umem.h b/lib/libspl/include/umem.h
index 49e9f9c14..ef9026009 100644
--- a/lib/libspl/include/umem.h
+++ b/lib/libspl/include/umem.h
@@ -36,6 +36,7 @@
  *
  * https://labs.omniti.com/trac/portableumem
  */
+#include <sys/debug.h>
 
 #include <stdlib.h>
 #include <stdio.h>
@@ -131,13 +132,13 @@ umem_zalloc(size_t size, int flags)
 }
 
 static inline void
-umem_free(void *ptr, size_t size)
+umem_free(void *ptr, size_t size __maybe_unused)
 {
 	free(ptr);
 }
 
 static inline void
-umem_nofail_callback(umem_nofail_callback_t *cb)
+umem_nofail_callback(umem_nofail_callback_t *cb __maybe_unused)
 {}
 
 static inline umem_cache_t *
@@ -199,7 +200,7 @@ umem_cache_free(umem_cache_t *cp, void *ptr)
 }
 
 static inline void
-umem_cache_reap_now(umem_cache_t *cp)
+umem_cache_reap_now(umem_cache_t *cp __maybe_unused)
 {
 }