diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c
index 48e8569b24..3f1d952635 100644
--- a/cmd/ztest/ztest.c
+++ b/cmd/ztest/ztest.c
@@ -1042,6 +1042,7 @@ ztest_pattern_set(void *buf, uint64_t size, uint64_t value)
 		*ip++ = value;
 }
 
+#ifndef NDEBUG
 static boolean_t
 ztest_pattern_match(void *buf, uint64_t size, uint64_t value)
 {
@@ -1054,6 +1055,7 @@ ztest_pattern_match(void *buf, uint64_t size, uint64_t value)
 
 	return (diff == 0);
 }
+#endif
 
 static void
 ztest_bt_generate(ztest_block_tag_t *bt, objset_t *os, uint64_t object,