diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
index 39dfdefec2c..05a9fca4bf6 100644
--- a/Modules/_ctypes/_ctypes.c
+++ b/Modules/_ctypes/_ctypes.c
@@ -1477,7 +1477,7 @@ SimpleType_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 	StgDictObject *stgdict;
 	PyObject *proto;
 	const char *proto_str;
-	int proto_len;
+	Py_ssize_t proto_len;
 	PyMethodDef *ml;
 	struct fielddesc *fmt;
 
diff --git a/Modules/_ctypes/libffi_msvc/prep_cif.c b/Modules/_ctypes/libffi_msvc/prep_cif.c
index 2650fa05254..cd623a1462c 100644
--- a/Modules/_ctypes/libffi_msvc/prep_cif.c
+++ b/Modules/_ctypes/libffi_msvc/prep_cif.c
@@ -163,7 +163,7 @@ ffi_status ffi_prep_cif(/*@out@*/ /*@partial@*/ ffi_cif *cif,
 	    bytes = ALIGN(bytes, (*ptr)->alignment);
 	  
 #endif
-	  bytes += STACK_ARG_SIZE((*ptr)->size);
+	  bytes += (unsigned)STACK_ARG_SIZE((*ptr)->size);
 	}
 #endif
     }