diff --git a/arch/AArch64.S b/arch/AArch64.S
index a002b0d..c7d7f4f 100644
--- a/arch/AArch64.S
+++ b/arch/AArch64.S
@@ -149,6 +149,29 @@ cu_memzero:
     ret
 
 cu_memtest:
+    // x0 - src, x1 - size
+    mov x2, x1, lsr #3
+    tst x2, x2
+    beq .test1_
+.test8:
+    ldr x3, [x0], #8
+    cmp x3, xzr
+    bne .testnot
+    subs x2, x2, #1
+    bne .test8
+.test1_:
+    and x2, x1, #7
+    beq .testok
+.test1:
+    ldrb w3, [x0], #1
+    cmp w3, wzr
+    bne .testnot
+    subs x2, x2, #1
+    bne .test1
+.testok:
+    mov x0, xzr
+    ret
+.testnot:
     ret
 
 cu_va_start:
diff --git a/test.c b/test.c
index 3f4aee3..02a81b2 100644
--- a/test.c
+++ b/test.c
@@ -163,6 +163,9 @@ int main()
     printf("value_offset\t%u\n", value_offset(CU_STRUCT(test_s), 5, &test));
     printf("value_size\t%u\n", value_size(CU_STRUCT(test_s), 5, &test));
 
+    char c0 = 0;
+    printf("cu_memset\tc0\t%p\n", cu_memtest(&c0, 1));
+
     printf("[va_list]\n");
     va_test(1337, 1, 2, 3, 4, 5);