2 files changed, 4 insertions, 2 deletions
diff --git a/main.c b/main.c
index a36250a..fc56947 100644
--- a/main.c
+++ b/main.c
@@ -498,9 +498,9 @@ static void assemblemem(Memarg *memarg, uint8_t rexw, VarBytes prefix,
   if (memarg->index == ASM_NO_REG) {
     index = 4;
   } else {
+    if (memarg->index == ASM_RSP)
+      lfatal("rsp cannot be used as an index");
     index = regbits(memarg->index);
-    if ((index & 7) == 4)
-      lfatal("sp cannot be used as an index");
   }
 
   /* If our base is a bp register, we must use the index instead. */
diff --git a/test/test.sh b/test/test.sh
index a916740..e81b051 100644
--- a/test/test.sh
+++ b/test/test.sh
@@ -33,6 +33,8 @@ t () {
 t "callq *%rax"
 t "callq *%r10"
 
+t "movb %r11b, (%rsi, %r12, 1)"
+
 t "cvtsi2sd %rax, %xmm1"
 t "cvtsi2sd %rax, %xmm10"
 t "cvtsi2sd (%rax), %xmm1"