diff --git a/Objects/genobject.c b/Objects/genobject.c
index 26e27cc..6998967 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -357,7 +357,7 @@ _PyGen_yf(PyGenObject *gen)
             return NULL;
         }
 
-        if (code[f->f_lasti + sizeof(_Py_CODEUNIT)] != YIELD_FROM)
+        if (code[(f->f_lasti+1)*sizeof(_Py_CODEUNIT)] != YIELD_FROM)
             return NULL;
         assert(f->f_stackdepth > 0);
         yf = f->f_valuestack[f->f_stackdepth-1];
@@ -481,7 +481,7 @@ _gen_throw(PyGenObject *gen, int close_on_genexit,
             Py_DECREF(ret);
             /* Termination repetition of YIELD_FROM */
             assert(gen->gi_frame->f_lasti >= 0);
-            gen->gi_frame->f_lasti += sizeof(_Py_CODEUNIT);
+            gen->gi_frame->f_lasti += 1;
             if (_PyGen_FetchStopIterationValue(&val) == 0) {
                 ret = gen_send(gen, val);
                 Py_DECREF(val);