diff --git a/src/rtdisasm.c b/src/rtdisasm.c
index e2f4061..05f6c49 100644
--- a/src/rtdisasm.c
+++ b/src/rtdisasm.c
@@ -100,7 +100,7 @@ static const instruction_t* find_instruction(const uint8_t* cur, unsigned type,
             continue;
         }
 
-        if (ins->config.has_modrm)
+        if (ins->config.has_opreg)
         {
             // instruction encoding employs register embedded into last opcode byte
             // so we need to apply bit mask
diff --git a/src/rtdisasm_test_data.s b/src/rtdisasm_test_data.s
index 7e19828..b535e40 100644
--- a/src/rtdisasm_test_data.s
+++ b/src/rtdisasm_test_data.s
@@ -3,8 +3,7 @@
 .globl test_1_end
 
 test_1:
-    lock
-    mov %gs:(%rbx), %rax
+    push %rbp
 
     nop # target that rtdisasm must reach
 test_1_end: