diff --git a/Modules/_decimal/_decimal.c b/Modules/_decimal/_decimal.c
index 1c34ba0..846b2a8 100644
--- a/Modules/_decimal/_decimal.c
+++ b/Modules/_decimal/_decimal.c
@@ -428,7 +428,7 @@
         return DEC_INVALID_SIGNALS;
     }
 
-    if (PyDict_GET_SIZE(val) != SIGNAL_MAP_LEN) {
+    if (PyDict_Size(val) != SIGNAL_MAP_LEN) {
         PyErr_SetString(PyExc_KeyError,
             "invalid signal dict");
         return DEC_INVALID_SIGNALS;