diff --git a/selfdrive/pandad/pandad_api_impl.pyx b/selfdrive/pandad/pandad_api_impl.pyx
index 7bc3b6c2d9b612..163fb5f7ead1f8 100644
--- a/selfdrive/pandad/pandad_api_impl.pyx
+++ b/selfdrive/pandad/pandad_api_impl.pyx
@@ -28,16 +28,17 @@ cdef extern from "can_list_to_can_capnp.cc":
   void can_capnp_to_can_list_cpp(const vector[string] &strings, vector[CanData] &can_data, bool sendcan)
 
 def can_list_to_can_capnp(can_msgs, msgtype='can', valid=True):
+  cdef can_frame *f
   cdef vector[can_frame] can_list
-  can_list.reserve(len(can_msgs))
 
-  cdef can_frame f
+  can_list.reserve(len(can_msgs))
   for can_msg in can_msgs:
+    f = &(can_list.emplace_back())
     f.address = can_msg[0]
     f.busTime = can_msg[1]
     f.dat = can_msg[2]
     f.src = can_msg[3]
-    can_list.push_back(f)
+
   cdef string out
   can_list_to_can_capnp_cpp(can_list, out, msgtype == 'sendcan', valid)
   return out
@@ -45,9 +46,10 @@ def can_list_to_can_capnp(can_msgs, msgtype='can', valid=True):
 def can_capnp_to_list(strings, sendcan=False):
   cdef vector[CanData] data
   can_capnp_to_can_list_cpp(strings, data, sendcan)
+
   result = []
-  cdef vector[CanData].iterator it = data.begin()
   cdef CanData *d
+  cdef vector[CanData].iterator it = data.begin()
   while it != data.end():
     d = &deref(it)
     frames = [[f.address, 0, (<char *>&f.dat[0])[:f.dat.size()], f.src] for f in d.frames]