diff --git a/server/core/config_runtime.cc b/server/core/config_runtime.cc
index 83c2df2ed..ac0c1e627 100644
--- a/server/core/config_runtime.cc
+++ b/server/core/config_runtime.cc
@@ -21,6 +21,7 @@
 #include <set>
 #include <iterator>
 #include <algorithm>
+#include <vector>
 
 #include <maxscale/atomic.h>
 #include <maxscale/hk_heartbeat.h>
@@ -1132,6 +1133,28 @@ static bool is_valid_resource_body(json_t* json)
         runtime_error("No '%s' field defined", MXS_JSON_PTR_DATA);
         rval = false;
     }
+    else
+    {
+        // Check that the relationship JSON is well-formed
+        const std::vector<const char*> relations =
+        {
+            MXS_JSON_PTR_RELATIONSHIPS "/servers",
+            MXS_JSON_PTR_RELATIONSHIPS "/services",
+            MXS_JSON_PTR_RELATIONSHIPS "/monitors",
+            MXS_JSON_PTR_RELATIONSHIPS "/filters",
+        };
+
+        for (auto it = relations.begin(); it != relations.end(); it++)
+        {
+            json_t* j = mxs_json_pointer(json, *it);
+
+            if (j && !json_is_object(j))
+            {
+                runtime_error("Relationship '%s' is not an object",*it);
+                rval = false;
+            }
+        }
+    }
 
     return rval;
 }
@@ -1468,9 +1491,9 @@ static bool is_valid_relationship_body(json_t* json)
         runtime_error("Field '%s' is not defined", MXS_JSON_PTR_DATA);
         rval = false;
     }
-    else if (!json_is_array(obj))
+    else if (!json_is_array(obj) && !json_is_null(obj))
     {
-        runtime_error("Field '%s' is not an array", MXS_JSON_PTR_DATA);
+        runtime_error("Field '%s' is not an array or null", MXS_JSON_PTR_DATA);
         rval = false;
     }
 
diff --git a/server/core/test/rest-api/test/monitor.js b/server/core/test/rest-api/test/monitor.js
index 893b36b38..4c3b41909 100644
--- a/server/core/test/rest-api/test/monitor.js
+++ b/server/core/test/rest-api/test/monitor.js
@@ -47,11 +47,18 @@ describe("Monitor Relationships", function() {
             .should.be.fulfilled
     })
 
+    it("remove with malformed relationships", function() {
+        var mon = {data: {relationships: {servers: null}}}
+        return request.patch(base_url + "/monitors/MariaDB-Monitor", {json: mon})
+            .should.be.rejected
+            .then(() => request.get(base_url + "/monitors/MariaDB-Monitor", { json: true }))
+            .then((res) => {
+                res.data.relationships.should.have.keys("servers")
+            })
+    });
+
     it("remove relationships from old monitor", function() {
-        var mon = { data: {
-            relationships: {
-                servers: null
-            }}}
+        var mon = {data: {relationships: {servers: {data: null}}}}
         return request.patch(base_url + "/monitors/MariaDB-Monitor", {json: mon})
         .then(() => request.get(base_url + "/monitors/MariaDB-Monitor", { json: true }))
         .then((res) => {
@@ -79,7 +86,7 @@ describe("Monitor Relationships", function() {
     });
 
     it("move relationships back to old monitor", function() {
-        var mon = {data: {relationships: {servers: null}}}
+        var mon = {data: {relationships: {servers: {data: null}}}}
         return request.patch(base_url + "/monitors/" + monitor.data.id, {json: mon})
             .then(() => request.get(base_url + "/monitors/" + monitor.data.id, { json: true }))
             .then((res) => {
@@ -125,7 +132,7 @@ describe("Monitor Relationships", function() {
     });
 
     it("bad request body with `relationships` endpoint should be rejected", function() {
-        return request.patch(base_url + "/monitors/" + monitor.data.id + "/relationships/servers", {json: {data: null}})
+        return request.patch(base_url + "/monitors/" + monitor.data.id + "/relationships/servers", {json: {servers: null}})
             .should.be.rejected
     })
 
@@ -137,7 +144,7 @@ describe("Monitor Relationships", function() {
             { id: "server4", type: "servers" }
         ]}
 
-        return request.patch(base_url + "/monitors/" + monitor.data.id + "/relationships/servers", {json: {data: []}})
+        return request.patch(base_url + "/monitors/" + monitor.data.id + "/relationships/servers", {json: {data: null}})
         .then(() => request.patch(base_url + "/monitors/MariaDB-Monitor/relationships/servers", {json: old}))
         .then(() => request.get(base_url + "/monitors/MariaDB-Monitor", { json: true }))
         .then((res) => {
diff --git a/server/core/test/rest-api/test/server.js b/server/core/test/rest-api/test/server.js
index dcc7671f7..5ed501358 100644
--- a/server/core/test/rest-api/test/server.js
+++ b/server/core/test/rest-api/test/server.js
@@ -80,13 +80,13 @@ describe("Server Relationships", function() {
     });
 
     it("bad request body with `relationships` endpoint should be rejected", function() {
-        var body = {data: null}
+        var body = {monitors: null}
         return request.patch(base_url + "/servers/" + rel_server.data.id + "/relationships/monitors", { json: body })
             .should.be.rejected
     });
 
     it("remove relationships with `relationships` endpoint", function() {
-        var body = {data: []}
+        var body = {data: null}
         return request.patch(base_url + "/servers/" + rel_server.data.id + "/relationships/monitors", { json: body })
             .then(() => request.get(base_url + "/servers/" + rel_server.data.id, {json: true}))
             .then((res) => {
@@ -96,9 +96,16 @@ describe("Server Relationships", function() {
             })
     });
 
-    it("remove relationships", function() {
+    it("remove with malformed relationships", function() {
         rel_server.data.relationships["services"] = null
         rel_server.data.relationships["monitors"] = null
+        return request.patch(base_url + "/servers/" + rel_server.data.id, {json: rel_server})
+            .should.be.rejected
+    });
+
+    it("remove relationships", function() {
+        rel_server.data.relationships["services"] = {data: null}
+        rel_server.data.relationships["monitors"] = {data: null}
         return request.patch(base_url + "/servers/" + rel_server.data.id, {json: rel_server})
             .should.be.fulfilled
     });
diff --git a/server/core/test/rest-api/test/service.js b/server/core/test/rest-api/test/service.js
index 61a8fb4d4..7df8de961 100644
--- a/server/core/test/rest-api/test/service.js
+++ b/server/core/test/rest-api/test/service.js
@@ -64,12 +64,12 @@ describe("Service", function() {
     });
 
     it("bad request body with `relationships` endpoint should be rejected", function() {
-        return request.patch(base_url + "/services/RW-Split-Router/relationships/servers", {json: {data: null}})
+        return request.patch(base_url + "/services/RW-Split-Router/relationships/servers", {json: {servers: null}})
             .should.be.rejected
     })
 
     it("remove service relationship via `relationships` endpoint", function() {
-        return request.patch(base_url + "/services/RW-Split-Router/relationships/servers", { json: {data: []}})
+        return request.patch(base_url + "/services/RW-Split-Router/relationships/servers", { json: {data: null}})
             .then(() => request.get(base_url + "/services/RW-Split-Router", { json: true }))
             .then((res) => {
                 res.data.relationships.should.not.have.keys("servers")