diff --git a/test/null_vfd_plugin.c b/test/null_vfd_plugin.c
index 8031484d3d5..f41da00f057 100644
--- a/test/null_vfd_plugin.c
+++ b/test/null_vfd_plugin.c
@@ -75,42 +75,73 @@ static const H5FD_class_t H5FD_null_g = {
 static H5FD_t *
 H5FD_null_open(const char *name, unsigned flags, hid_t fapl_id, haddr_t maxaddr)
 {
+    (void)name;
+    (void)flags;
+    (void)fapl_id;
+    (void)maxaddr;
+
     return NULL;
 }
 
 static herr_t
 H5FD_null_close(H5FD_t *_file)
 {
+    (void)_file;
+
     return 0;
 }
 
 static herr_t
 H5FD_null_read(H5FD_t *_file, H5FD_mem_t type, hid_t dxpl_id, haddr_t addr, size_t size, void *buf)
 {
+    (void)_file;
+    (void)type;
+    (void)dxpl_id;
+    (void)addr;
+    (void)size;
+    (void)buf;
+
     return 0;
 }
 
 static herr_t
 H5FD_null_write(H5FD_t *_file, H5FD_mem_t type, hid_t dxpl_id, haddr_t addr, size_t size, const void *buf)
 {
+    (void)_file;
+    (void)type;
+    (void)dxpl_id;
+    (void)addr;
+    (void)size;
+    (void)buf;
+
     return 0;
 }
 
 static haddr_t
 H5FD_null_get_eoa(const H5FD_t *_file, H5FD_mem_t type)
 {
+    (void)_file;
+    (void)type;
+
     return HADDR_UNDEF;
 }
 
 static herr_t
 H5FD_null_set_eoa(H5FD_t *_file, H5FD_mem_t type, haddr_t addr)
 {
+    (void)_file;
+    (void)type;
+    (void)addr;
+
     return 0;
 }
 
 static haddr_t
 H5FD_null_get_eof(const H5FD_t *_file, H5FD_mem_t type)
 {
+    (void)_file;
+    (void)type;
+
     return HADDR_UNDEF;
 }