diff --git a/src/devices/cpu/patinhofeio/patinho_feio.cpp b/src/devices/cpu/patinhofeio/patinho_feio.cpp
index eac67e79c9b..595a62db6b6 100644
--- a/src/devices/cpu/patinhofeio/patinho_feio.cpp
+++ b/src/devices/cpu/patinhofeio/patinho_feio.cpp
@@ -95,6 +95,7 @@ void patinho_feio_cpu_device::execute_run()
         if ((! m_run)){
             m_icount = 0;   /* if processor is stopped, just burn cycles */
         } else {
+            m_idx = READ_INDEX_REG();
             execute_instruction();
             m_icount --;
         }