diff -up data/references/Curl.constants.json.old data/references/Curl.constants.json
--- data/references/Curl.constants.json.old	2016-01-09 15:10:57.792505666 +0100
+++ data/references/Curl.constants.json	2016-01-09 15:12:39.665949126 +0100
@@ -3874,7 +3874,8 @@
         "ext_max": "",
         "php_min": "5.5.0",
         "php_max": "",
-        "php_excludes": ""
+        "php_excludes": "",
+        "optional": true
     },
     {
         "ext_name_fk": 9,
@@ -3883,7 +3884,8 @@
         "ext_max": "",
         "php_min": "5.5.0",
         "php_max": "",
-        "php_excludes": ""
+        "php_excludes": "",
+        "optional": true
     },
     {
         "ext_name_fk": 9,
@@ -3892,7 +3894,8 @@
         "ext_max": "",
         "php_min": "5.5.0",
         "php_max": "",
-        "php_excludes": ""
+        "php_excludes": "",
+        "optional": true
     },
     {
         "ext_name_fk": 9,
@@ -3901,7 +3904,8 @@
         "ext_max": "",
         "php_min": "5.5.0",
         "php_max": "",
-        "php_excludes": ""
+        "php_excludes": "",
+        "optional": true
     },
     {
         "ext_name_fk": 9,
@@ -3911,7 +3915,8 @@
         "php_min": "5.5.19RC1",
         "php_max": "",
         "php_excludes": "5.6.0, 5.6.0RC1, 5.6.0RC2, 5.6.0RC3, 5.6.0RC4, 5.6.1, 5.6.1RC1, 5.6.2",
-        "lib_curl": "~7.34"
+        "lib_curl": "~7.34",
+        "optional": true
     },
     {
         "ext_name_fk": 9,
@@ -3921,7 +3926,8 @@
         "php_min": "5.5.19RC1",
         "php_max": "",
         "php_excludes": "5.6.0, 5.6.0RC1, 5.6.0RC2, 5.6.0RC3, 5.6.0RC4, 5.6.1, 5.6.1RC1, 5.6.2",
-        "lib_curl": "~7.34"
+        "lib_curl": "~7.34",
+        "optional": true
     },
     {
         "ext_name_fk": 9,
@@ -3931,7 +3937,8 @@
         "php_min": "5.5.19RC1",
         "php_max": "",
         "php_excludes": "5.6.0, 5.6.0RC1, 5.6.0RC2, 5.6.0RC3, 5.6.0RC4, 5.6.1, 5.6.1RC1, 5.6.2",
-        "lib_curl": "~7.34"
+        "lib_curl": "~7.34",
+        "optional": true
     },
     {
         "ext_name_fk": 9,