diff --git a/psycopg/connection_type.c b/psycopg/connection_type.c
index 9cdd640f..374d34f8 100644
--- a/psycopg/connection_type.c
+++ b/psycopg/connection_type.c
@@ -701,8 +701,8 @@ psyco_conn_get_parameter_status(connectionObject *self, PyObject *args)
 static PyObject *
 psyco_conn_lobject(connectionObject *self, PyObject *args, PyObject *keywds)
 {
-    Oid oid=InvalidOid, new_oid=InvalidOid;
-    char *new_file = NULL;
+    int oid = (int)InvalidOid, new_oid = (int)InvalidOid;
+    const char *new_file = NULL;
     const char *smode = "";
     PyObject *factory = (PyObject *)&lobjectType;
     PyObject *obj;
diff --git a/psycopg/lobject_type.c b/psycopg/lobject_type.c
index a55272ca..625a2939 100644
--- a/psycopg/lobject_type.c
+++ b/psycopg/lobject_type.c
@@ -373,7 +373,7 @@ lobject_dealloc(PyObject* obj)
 static int
 lobject_init(PyObject *obj, PyObject *args, PyObject *kwds)
 {
-    Oid oid=InvalidOid, new_oid=InvalidOid;
+    int oid = (int)InvalidOid, new_oid = (int)InvalidOid;
     const char *smode = "";
     const char *new_file = NULL;
     PyObject *conn;
@@ -383,7 +383,7 @@ lobject_init(PyObject *obj, PyObject *args, PyObject *kwds)
         return -1;
 
     return lobject_setup((lobjectObject *)obj,
-        (connectionObject *)conn, oid, smode, new_oid, new_file);
+        (connectionObject *)conn, (Oid)oid, smode, (Oid)new_oid, new_file);
 }
 
 static PyObject *
diff --git a/psycopg/typecast.c b/psycopg/typecast.c
index 9c36b02b..8504631b 100644
--- a/psycopg/typecast.c
+++ b/psycopg/typecast.c
@@ -468,7 +468,7 @@ typecast_repr(PyObject *self)
 static PyObject *
 typecast_call(PyObject *obj, PyObject *args, PyObject *kwargs)
 {
-    char *string;
+    const char *string;
     Py_ssize_t length;
     PyObject *cursor;