diff --git a/psycopg/adapter_list.c b/psycopg/adapter_list.c
index 2ce2e604..b6022bd5 100644
--- a/psycopg/adapter_list.c
+++ b/psycopg/adapter_list.c
@@ -155,7 +155,7 @@ static PyMethodDef listObject_methods[] = {
 /* initialization and finalization methods */
 
 static int
-list_setup(listObject *self, PyObject *obj, char *enc)
+list_setup(listObject *self, PyObject *obj, const char *enc)
 {
     Dprintf("list_setup: init list object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -198,7 +198,7 @@ static int
 list_init(PyObject *obj, PyObject *args, PyObject *kwds)
 {
     PyObject *l;
-    char *enc = "latin-1"; /* default encoding as in Python */
+    const char *enc = "latin-1"; /* default encoding as in Python */
 
     if (!PyArg_ParseTuple(args, "O|s", &l, &enc))
         return -1;
@@ -297,7 +297,7 @@ PyObject *
 psyco_List(PyObject *module, PyObject *args)
 {
     PyObject *str;
-    char *enc = "latin-1"; /* default encoding as in Python */
+    const char *enc = "latin-1"; /* default encoding as in Python */
 
     if (!PyArg_ParseTuple(args, "O|s", &str, &enc))
         return NULL;
diff --git a/psycopg/adapter_qstring.c b/psycopg/adapter_qstring.c
index cebb5216..3684039b 100644
--- a/psycopg/adapter_qstring.c
+++ b/psycopg/adapter_qstring.c
@@ -110,7 +110,7 @@ qstring_quote(qstringObject *self)
         /* note that enc is a borrowed reference */
 
         if (enc) {
-            char *s = PyString_AsString(enc);
+            const char *s = PyString_AsString(enc);
             Dprintf("qstring_quote: encoding unicode object to %s", s);
             str = PyUnicode_AsEncodedString(self->wrapped, s, NULL);
             Dprintf("qstring_quote: got encoded object at %p", str);
@@ -267,7 +267,7 @@ static PyMethodDef qstringObject_methods[] = {
 /* initialization and finalization methods */
 
 static int
-qstring_setup(qstringObject *self, PyObject *str, char *enc)
+qstring_setup(qstringObject *self, PyObject *str, const char *enc)
 {
     Dprintf("qstring_setup: init qstring object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -313,7 +313,7 @@ static int
 qstring_init(PyObject *obj, PyObject *args, PyObject *kwds)
 {
     PyObject *str;
-    char *enc = "latin-1"; /* default encoding as in Python */
+    const char *enc = "latin-1"; /* default encoding as in Python */
 
     if (!PyArg_ParseTuple(args, "O|s", &str, &enc))
         return -1;
@@ -413,7 +413,7 @@ PyObject *
 psyco_QuotedString(PyObject *module, PyObject *args)
 {
     PyObject *str;
-    char *enc = "latin-1"; /* default encoding as in Python */
+    const char *enc = "latin-1"; /* default encoding as in Python */
 
     if (!PyArg_ParseTuple(args, "O|s", &str, &enc))
         return NULL;
diff --git a/psycopg/connection_int.c b/psycopg/connection_int.c
index 2cc7818e..c5ba1ece 100644
--- a/psycopg/connection_int.c
+++ b/psycopg/connection_int.c
@@ -61,20 +61,20 @@ conn_connect(connectionObject *self)
 {
     PGconn *pgconn;
     PGresult *pgres;
-    char *data, *tmp;
+    const char *data, *tmp;
     const char *scs;    /* standard-conforming strings */
     size_t i;
 
     /* we need the initial date style to be ISO, for typecasters; if the user
        later change it, she must know what she's doing... */
-    const char *datestyle = "SET DATESTYLE TO 'ISO'";
-    const char *encoding  = "SHOW client_encoding";
-    const char *isolevel  = "SHOW default_transaction_isolation";
+    const char datestyle[] = "SET DATESTYLE TO 'ISO'";
+    const char encoding[]  = "SHOW client_encoding";
+    const char isolevel[]  = "SHOW default_transaction_isolation";
 
-    const char *lvl1a = "read uncommitted";
-    const char *lvl1b = "read committed";
-    const char *lvl2a = "repeatable read";
-    const char *lvl2b = "serializable";
+    const char lvl1a[] = "read uncommitted";
+    const char lvl1b[] = "read committed";
+    const char lvl2a[] = "repeatable read";
+    const char lvl2b[] = "serializable";
 
     Py_BEGIN_ALLOW_THREADS;
     pgconn = PQconnectdb(self->dsn);
diff --git a/psycopg/connection_type.c b/psycopg/connection_type.c
index 92a06863..38ca5f90 100644
--- a/psycopg/connection_type.c
+++ b/psycopg/connection_type.c
@@ -49,7 +49,7 @@
 static PyObject *
 psyco_conn_cursor(connectionObject *self, PyObject *args, PyObject *keywds)
 {
-    char *name = NULL;
+    const char *name = NULL;
     PyObject *obj, *factory = NULL;
 
     static char *kwlist[] = {"name", "cursor_factory", NULL};
@@ -186,7 +186,8 @@ psyco_conn_set_isolation_level(connectionObject *self, PyObject *args)
 static PyObject *
 psyco_conn_set_client_encoding(connectionObject *self, PyObject *args)
 {
-    char *buffer, *enc = NULL;
+    const char *enc = NULL;
+    char *buffer;
     size_t i, j;
 
     EXC_IF_CONN_CLOSED(self);
@@ -313,7 +314,7 @@ static struct PyGetSetDef connectionObject_getsets[] = {
 /* initialization and finalization methods */
 
 static int
-connection_setup(connectionObject *self, char *dsn)
+connection_setup(connectionObject *self, const char *dsn)
 {
     char *pos;
     int res;
@@ -389,7 +390,7 @@ connection_dealloc(PyObject* obj)
 static int
 connection_init(PyObject *obj, PyObject *args, PyObject *kwds)
 {
-    char *dsn;
+    const char *dsn;
 
     if (!PyArg_ParseTuple(args, "s", &dsn))
         return -1;
diff --git a/psycopg/cursor_type.c b/psycopg/cursor_type.c
index 083826f1..a17847ea 100644
--- a/psycopg/cursor_type.c
+++ b/psycopg/cursor_type.c
@@ -371,7 +371,7 @@ _psyco_curs_execute(cursorObject *self,
                 if (PyObject_HasAttrString(arg, "args")) {
                     PyObject *args = PyObject_GetAttrString(arg, "args");
                     PyObject *str = PySequence_GetItem(args, 0);
-                    char *s = PyString_AS_STRING(str);
+                    const char *s = PyString_AS_STRING(str);
 
                     Dprintf("psyco_curs_execute:     -> %s", s);
 
@@ -586,7 +586,7 @@ psyco_curs_mogrify(cursorObject *self, PyObject *args, PyObject *kwargs)
                 if (PyObject_HasAttrString(arg, "args")) {
                     PyObject *args = PyObject_GetAttrString(arg, "args");
                     PyObject *str = PySequence_GetItem(args, 0);
-                    char *s = PyString_AS_STRING(str);
+                    const char *s = PyString_AS_STRING(str);
 
                     Dprintf("psyco_curs_execute:     -> %s", s);
 
@@ -675,7 +675,7 @@ _psyco_curs_buildrow_fill(cursorObject *self, PyObject *res,
                           int row, int n, int istuple)
 {
     int i, len;
-    unsigned char *str;
+    const char *str;
     PyObject *val;
 
     for (i=0; i < n; i++) {
@@ -684,14 +684,14 @@ _psyco_curs_buildrow_fill(cursorObject *self, PyObject *res,
             len = 0;
         }
         else {
-            str = (unsigned char*)PQgetvalue(self->pgres, row, i);
+            str = PQgetvalue(self->pgres, row, i);
             len = PQgetlength(self->pgres, row, i);
         }
 
         Dprintf("_psyco_curs_buildrow: row %ld, element %d, len %d",
                 self->row, i, len);
 
-        val = typecast_cast(PyTuple_GET_ITEM(self->casts, i), (char*)str, len,
+        val = typecast_cast(PyTuple_GET_ITEM(self->casts, i), str, len,
                             (PyObject*)self);
 
         if (val) {
@@ -935,7 +935,8 @@ psyco_curs_fetchall(cursorObject *self, PyObject *args)
 static PyObject *
 psyco_curs_callproc(cursorObject *self, PyObject *args, PyObject *kwargs)
 {
-    char *procname = NULL, *sql = NULL;
+    const char *procname = NULL;
+    char *sql = NULL;
     long int async = 0;
     Py_ssize_t procname_len, i, nparameters = 0, sl = 0;
     PyObject *parameters = Py_None;
@@ -1055,7 +1056,7 @@ static PyObject *
 psyco_curs_scroll(cursorObject *self, PyObject *args, PyObject *kwargs)
 {
     int value, newpos;
-    char *mode = "relative";
+    const char *mode = "relative";
 
     static char *kwlist[] = {"value", "mode", NULL};
 
@@ -1186,8 +1187,8 @@ static PyObject *
 psyco_curs_copy_from(cursorObject *self, PyObject *args, PyObject *kwargs)
 {
     char query[DEFAULT_COPYBUFF];
-    char *table_name;
-    char *sep = "\t", *null = NULL;
+    const char *table_name;
+    const char *sep = "\t", *null = NULL;
     Py_ssize_t bufsize = DEFAULT_COPYBUFF;
     PyObject *file, *columns = NULL, *res = NULL;
     char columnlist[DEFAULT_COPYBUFF];
@@ -1260,8 +1261,8 @@ psyco_curs_copy_to(cursorObject *self, PyObject *args, PyObject *kwargs)
 {
     char query[DEFAULT_COPYBUFF];
     char columnlist[DEFAULT_COPYBUFF];
-    char *table_name;
-    char *sep = "\t", *null = NULL;
+    const char *table_name;
+    const char *sep = "\t", *null = NULL;
     PyObject *file, *columns = NULL, *res = NULL;
 
     static char *kwlist[] = {"file", "table", "sep", "null", "columns", NULL};
@@ -1570,7 +1571,7 @@ static struct PyGetSetDef cursorObject_getsets[] = {
 /* initialization and finalization methods */
 
 static int
-cursor_setup(cursorObject *self, connectionObject *conn, char *name)
+cursor_setup(cursorObject *self, connectionObject *conn, const char *name)
 {
     Dprintf("cursor_setup: init cursor object at %p", self);
     Dprintf("cursor_setup:     parameters: name = %s, conn = %p", name, conn);
@@ -1655,7 +1656,7 @@ cursor_dealloc(PyObject* obj)
 static int
 cursor_init(PyObject *obj, PyObject *args, PyObject *kwds)
 {
-    char *name = NULL;
+    const char *name = NULL;
     PyObject *conn;
 
     if (!PyArg_ParseTuple(args, "O|s", &conn, &name))
diff --git a/psycopg/psycopgmodule.c b/psycopg/psycopgmodule.c
index a212ba4b..b74abdce 100644
--- a/psycopg/psycopgmodule.c
+++ b/psycopg/psycopgmodule.c
@@ -93,7 +93,7 @@ int psycopg_debug_enabled = 0;
 ":rtype: `extensions.connection`"
 
 static size_t
-_psyco_connect_fill_dsn(char *dsn, char *kw, char *v, size_t i)
+_psyco_connect_fill_dsn(char *dsn, const char *kw, const char *v, size_t i)
 {
     strcpy(&dsn[i], kw); i += strlen(kw);
     strcpy(&dsn[i], v); i += strlen(v);
@@ -108,9 +108,10 @@ psyco_connect(PyObject *self, PyObject *args, PyObject *keywds)
 
     size_t idsn=-1;
     int iport=-1;
-    char *dsn_static=NULL, *dsn_dynamic=NULL;
-    char *database=NULL, *user=NULL, *password=NULL;
-    char *host=NULL, *sslmode=NULL;
+    const char *dsn_static = NULL;
+    char *dsn_dynamic=NULL;
+    const char *database=NULL, *user=NULL, *password=NULL;
+    const char *host=NULL, *sslmode=NULL;
     char port[16];
 
     static char *kwlist[] = {"dsn", "database", "host", "port",
@@ -415,7 +416,7 @@ static struct {
     char *name;
     PyObject **exc;
     PyObject **base;
-    char *docstr;
+    const char *docstr;
 } exctable[] = {
     { "psycopg2.Error", &Error, 0, Error_doc },
     { "psycopg2.Warning", &Warning, 0, Warning_doc },