diff --git a/UnitTests/HttpInterface/api-collection-mmfiles-spec.rb b/UnitTests/HttpInterface/api-collection-mmfiles-spec.rb
index 98616b533f..2adb3368ee 100644
--- a/UnitTests/HttpInterface/api-collection-mmfiles-spec.rb
+++ b/UnitTests/HttpInterface/api-collection-mmfiles-spec.rb
@@ -786,6 +786,51 @@ describe ArangoDB do
 ################################################################################
 
     context "properties:" do
+      it "changing the journalSize to null" do
+        cn = "UnitTestsCollectionBasics"
+        ArangoDB.drop_collection(cn)
+        cid = ArangoDB.create_collection(cn)
+
+        cmd = api + "/" + cn + "/properties"
+        body = "{ \"journalSize\" : 1048576 }"
+        doc = ArangoDB.log_put("#{prefix}-properties-journalSize", cmd, :body => body)
+        doc.code.should eq(200)
+
+        doc = ArangoDB.log_get("#{prefix}-properties-journalSize", cmd)
+        doc.code.should eq(200)
+        doc.parsed_response['error'].should eq(false)
+        doc.parsed_response['journalSize'].should eq(1048576)
+        
+        body = "{ \"journalSize\" : 8388608 }"
+        doc = ArangoDB.log_put("#{prefix}-properties-journalSize", cmd, :body => body)
+        doc.code.should eq(200)
+
+        doc = ArangoDB.log_get("#{prefix}-properties-journalSize", cmd)
+        doc.code.should eq(200)
+        doc.parsed_response['error'].should eq(false)
+        doc.parsed_response['journalSize'].should eq(8388608)
+        
+        body = "{ \"journalSize\" : null }"
+        doc = ArangoDB.log_put("#{prefix}-properties-journalSize", cmd, :body => body)
+        doc.code.should eq(200)
+
+        doc = ArangoDB.log_get("#{prefix}-properties-journalSize", cmd)
+        doc.code.should eq(200)
+        doc.parsed_response['error'].should eq(false)
+        doc.parsed_response['journalSize'].should eq(8388608)
+        
+        body = "{ }"
+        doc = ArangoDB.log_put("#{prefix}-properties-journalSize", cmd, :body => body)
+        doc.code.should eq(200)
+
+        doc = ArangoDB.log_get("#{prefix}-properties-journalSize", cmd)
+        doc.code.should eq(200)
+        doc.parsed_response['error'].should eq(false)
+        doc.parsed_response['journalSize'].should eq(8388608)
+
+        ArangoDB.drop_collection(cn)
+      end
+
       it "changing the properties of a collection by identifier" do
         cn = "UnitTestsCollectionBasics"
         ArangoDB.drop_collection(cn)
diff --git a/arangod/MMFiles/MMFilesCollection.cpp b/arangod/MMFiles/MMFilesCollection.cpp
index 8ed084e37a..3767f9b4de 100644
--- a/arangod/MMFiles/MMFilesCollection.cpp
+++ b/arangod/MMFiles/MMFilesCollection.cpp
@@ -144,11 +144,11 @@ arangodb::Result MMFilesCollection::updateProperties(VPackSlice const& slice,
   auto journalSlice = slice.get("journalSize");
 
   if (journalSlice.isNone()) {
-    // In some apis maximalSize is allowed instead
+    // In some APIs maximalSize is allowed instead
     journalSlice = slice.get("maximalSize");
   }
 
-  if (!journalSlice.isNone()) {
+  if (!journalSlice.isNone() && journalSlice.isNumber()) {
     TRI_voc_size_t toUpdate = journalSlice.getNumericValue<TRI_voc_size_t>();
     if (toUpdate < TRI_JOURNAL_MINIMAL_SIZE) {
       return {TRI_ERROR_BAD_PARAMETER, "<properties>.journalSize too small"};