diff --git a/include/maxscale/config.h b/include/maxscale/config.h
index 7c9cd5211..4fdc580a2 100644
--- a/include/maxscale/config.h
+++ b/include/maxscale/config.h
@@ -108,6 +108,7 @@ extern const char CN_AUTH_CONNECT_TIMEOUT[];
 extern const char CN_AUTH_READ_TIMEOUT[];
 extern const char CN_AUTH_WRITE_TIMEOUT[];
 extern const char CN_AUTO[];
+extern const char CN_CACHE_SIZE[];
 extern const char CN_CONNECTION_TIMEOUT[];
 extern const char CN_DUMP_LAST_STATEMENTS[];
 extern const char CN_DATA[];
diff --git a/server/core/config.cc b/server/core/config.cc
index ca51c4028..35e71c96a 100644
--- a/server/core/config.cc
+++ b/server/core/config.cc
@@ -87,6 +87,7 @@ const char CN_AUTH_CONNECT_TIMEOUT[]          = "auth_connect_timeout";
 const char CN_AUTH_READ_TIMEOUT[]             = "auth_read_timeout";
 const char CN_AUTH_WRITE_TIMEOUT[]            = "auth_write_timeout";
 const char CN_AUTO[]                          = "auto";
+const char CN_CACHE_SIZE[]                    = "cache_size";
 const char CN_CONNECTION_TIMEOUT[]            = "connection_timeout";
 const char CN_DATA[]                          = "data";
 const char CN_DEFAULT[]                       = "default";
diff --git a/server/core/config_runtime.cc b/server/core/config_runtime.cc
index 680086106..b5a2db53b 100644
--- a/server/core/config_runtime.cc
+++ b/server/core/config_runtime.cc
@@ -2541,39 +2541,7 @@ bool runtime_alter_maxscale_from_json(json_t* new_json)
     return rval;
 }
 
-bool validate_qc_json(json_t* json)
-{
-    json_t* param = mxs_json_pointer(json, MXS_JSON_PTR_PARAMETERS);
-    bool rval = false;
-
-    if (param && json_is_object(param))
-    {
-        rval = runtime_is_count_or_null(param, "cache_size");
-    }
-
-    return rval;
-}
-
-// TODO: Expose everything needed so that this function could be
-// TODO: part of the query classifier API. 
 bool runtime_alter_qc_from_json(json_t* json)
 {
-    bool rval = false;
-
-    if (validate_qc_json(json))
-    {
-        rval = true;
-
-        json_t* param = mxs_json_pointer(json, MXS_JSON_PTR_PARAMETERS);
-        json_t* value;
-
-        if ((value = mxs_json_pointer(param, "cache_size")))
-        {
-            QC_CACHE_PROPERTIES cache_properties = { json_integer_value(value) };
-
-            qc_set_cache_properties(&cache_properties);
-        }
-    }
-
-    return rval;
+    return qc_alter_from_json(json);
 }
diff --git a/server/core/internal/query_classifier.hh b/server/core/internal/query_classifier.hh
index f17d510db..129b4d059 100644
--- a/server/core/internal/query_classifier.hh
+++ b/server/core/internal/query_classifier.hh
@@ -38,12 +38,22 @@ typedef enum qc_trx_parse_using
 uint32_t qc_get_trx_type_mask_using(GWBUF* stmt, qc_trx_parse_using_t use);
 
 /**
- * Generic query classifier information.
+ * Common query classifier properties as JSON.
  *
  * @param zHost  The MaxScale host.
  *
- * @return A json object containing information.
+ * @return A json object containing properties.
  */
 std::unique_ptr<json_t> qc_as_json(const char* zHost);
 
+/**
+ * Alter common query classifier properties.
+ *
+ * @param pJson  A JSON object.
+ *
+ * @return True, if the object was valid and parameters could be changed,
+ *         false otherwise.
+ */
+bool qc_alter_from_json(json_t* pJson);
+
 MXS_END_DECLS
diff --git a/server/core/query_classifier.cc b/server/core/query_classifier.cc
index 3a6a6a4f5..e6d3f13fe 100644
--- a/server/core/query_classifier.cc
+++ b/server/core/query_classifier.cc
@@ -27,6 +27,7 @@
 #include <maxscale/platform.h>
 #include <maxscale/utils.h>
 
+#include "internal/config_runtime.h"
 #include "internal/modules.h"
 #include "internal/trxboundaryparser.hh"
 
@@ -1258,15 +1259,54 @@ json_t* qc_get_cache_stats_as_json()
 std::unique_ptr<json_t> qc_as_json(const char* zHost)
 {
     json_t* pParams = json_object();
-    json_object_set_new(pParams, "cache_size", json_integer(this_unit.cache_max_size()));
+    json_object_set_new(pParams, CN_CACHE_SIZE, json_integer(this_unit.cache_max_size()));
 
     json_t* pAttributes = json_object();
     json_object_set_new(pAttributes, CN_PARAMETERS, pParams);
 
     json_t* pSelf = json_object();
-    json_object_set_new(pSelf, CN_ID, json_string("query_classifier"));
-    json_object_set_new(pSelf, CN_TYPE, json_string("query_classifier"));
+    json_object_set_new(pSelf, CN_ID, json_string(CN_QUERY_CLASSIFIER));
+    json_object_set_new(pSelf, CN_TYPE, json_string(CN_QUERY_CLASSIFIER));
     json_object_set_new(pSelf, CN_ATTRIBUTES, pAttributes);
 
     return std::unique_ptr<json_t>(mxs_json_resource(zHost, MXS_JSON_API_QC, pSelf));
 }
+
+namespace
+{
+
+json_t* get_params(json_t* pJson)
+{
+    json_t* pParams = mxs_json_pointer(pJson, MXS_JSON_PTR_PARAMETERS);
+
+    if (pParams && json_is_object(pParams))
+    {
+        if (!runtime_is_count_or_null(pParams, CN_CACHE_SIZE))
+        {
+            pParams = nullptr;
+        }
+    }
+
+    return pParams;
+}
+
+}
+
+bool qc_alter_from_json(json_t* pJson)
+{
+    json_t* pParams = get_params(pJson);
+
+    if (pParams)
+    {
+        json_t* pValue;
+
+        if ((pValue = mxs_json_pointer(pParams, CN_CACHE_SIZE)))
+        {
+            QC_CACHE_PROPERTIES cache_properties = { json_integer_value(pValue) };
+
+            qc_set_cache_properties(&cache_properties);
+        }
+    }
+
+    return pParams != nullptr;
+}