diff --git a/src/crab/thumb/software_interrupt.cr b/src/crab/thumb/software_interrupt.cr
index 4699de7..bc21d1b 100644
--- a/src/crab/thumb/software_interrupt.cr
+++ b/src/crab/thumb/software_interrupt.cr
@@ -1,6 +1,6 @@
 module THUMB
   def thumb_software_interrupt(instr : Word) : Nil
-    lr = @r[15] - 4
+    lr = @r[15] - 2
     switch_mode CPU::Mode::SVC
     set_reg(14, lr)
     @cpsr.irq_disable = true