diff --git a/psycopg/adapter_pdecimal.c b/psycopg/adapter_pdecimal.c
index 25a7212d1..15ae13112 100644
--- a/psycopg/adapter_pdecimal.c
+++ b/psycopg/adapter_pdecimal.c
@@ -47,11 +47,24 @@ pdecimal_getquoted(pdecimalObject *self, PyObject *args)
         }
         goto output;
     }
-    else if (check) {
+
+    check = PyObject_CallMethod(self->wrapped, "is_nan", NULL);
+    if (check == Py_True) {
         res = Bytes_FromString("'NaN'::numeric");
         goto end;
     }
 
+    /* If the decimal is not finite and not NaN, it must be infinity,
+     * so all that is left is to check if it is positive or negative. */
+    check = PyObject_CallMethod(self->wrapped, "is_signed", NULL);
+    if (check == Py_True) {
+        res = Bytes_FromString("'-Infinity'::numeric");
+        goto end;
+    } else {
+        res = Bytes_FromString("'Infinity'::numeric");
+        goto end;
+    }
+
     /* is_finite() was introduced 2.5.1 < somewhere <= 2.5.4.
      * We assume we are here because we didn't find the method. */
     PyErr_Clear();
diff --git a/tests/test_types_basic.py b/tests/test_types_basic.py
index 31f0310d4..c3f615904 100755
--- a/tests/test_types_basic.py
+++ b/tests/test_types_basic.py
@@ -75,11 +75,11 @@ def testDecimal(self):
         self.failUnless(type(s) == decimal.Decimal,
                         "wrong decimal conversion: " + repr(s))
         s = self.execute("SELECT %s AS foo", (decimal.Decimal("infinity"),))
-        self.failUnless(str(s) == "NaN", "wrong decimal quoting: " + str(s))
+        self.failUnless(str(s) == "Infinity", "wrong decimal quoting: " + str(s))
         self.failUnless(type(s) == decimal.Decimal,
                         "wrong decimal conversion: " + repr(s))
         s = self.execute("SELECT %s AS foo", (decimal.Decimal("-infinity"),))
-        self.failUnless(str(s) == "NaN", "wrong decimal quoting: " + str(s))
+        self.failUnless(str(s) == "-Infinity", "wrong decimal quoting: " + str(s))
         self.failUnless(type(s) == decimal.Decimal,
                         "wrong decimal conversion: " + repr(s))