diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 8c01a62d92..20361b3a23 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -976,10 +976,7 @@ vm_getivar(VALUE obj, ID id, IC ic, struct rb_call_cache *cc, int is_attr)
 		    if (index < ROBJECT_NUMIV(obj)) {
 			val = ROBJECT_IVPTR(obj)[index];
 		    }
-                    if (is_attr) { /* call_info */
-                        cc->aux.index = (int)index + 1;
-                    }
-                    else { /* getinstancevariable */
+                    if (!is_attr) { /* getinstancevariable */
                         if (ic->ic_serial == RUBY_VM_CLASS_SERIAL_UNSET) {
                             /* set ic_serial only for the first time */
                             ic->ic_value.index = index;
@@ -990,7 +987,10 @@ vm_getivar(VALUE obj, ID id, IC ic, struct rb_call_cache *cc, int is_attr)
                                and to reduce the number of JIT cancellations by code generated for IC hit. */
                             ic->ic_serial = RUBY_VM_CLASS_SERIAL_INVALID;
                         }
-		    }
+                    }
+                    else { /* call_info */
+                        cc->aux.index = (int)index + 1;
+                    }
 		}
 	    }
 	}
@@ -1039,10 +1039,18 @@ vm_setivar(VALUE obj, ID id, VALUE val, IC ic, struct rb_call_cache *cc, int is_
 	    struct st_table *iv_index_tbl = ROBJECT_IV_INDEX_TBL(obj);
 
 	    if (iv_index_tbl && st_lookup(iv_index_tbl, (st_data_t)id, &index)) {
-		if (!is_attr) {
-		    ic->ic_value.index = index;
-		    ic->ic_serial = RCLASS_SERIAL(klass);
-		}
+                if (!is_attr) { /* setinstancevariable */
+                    if (ic->ic_serial == RUBY_VM_CLASS_SERIAL_UNSET) {
+                        /* set ic_serial only for the first time */
+                        ic->ic_value.index = index;
+                        ic->ic_serial = RCLASS_SERIAL(klass);
+                    }
+                    else if (ic->ic_serial != RUBY_VM_CLASS_SERIAL_INVALID) {
+                        /* never use cache for another class, to avoid race condition with MJIT worker
+                           and to reduce the number of JIT cancellations by code generated for IC hit. */
+                        ic->ic_serial = RUBY_VM_CLASS_SERIAL_INVALID;
+                    }
+                }
 		else if (index >= INT_MAX) {
 		    rb_raise(rb_eArgError, "too many instance variables");
 		}