diff --git a/app/Importer/AssetImporter.php b/app/Importer/AssetImporter.php
index 3623c6e484..a8fd712536 100644
--- a/app/Importer/AssetImporter.php
+++ b/app/Importer/AssetImporter.php
@@ -31,9 +31,8 @@ class AssetImporter extends ItemImporter
                     $this->item['custom_fields'][$customField->db_column_name()] = $customFieldValue;
                     $this->log('Custom Field '. $customField->name.': '.$customFieldValue);
                 } else {
-                    // This removes custom fields when updating if the column doesn't exist in file.
-                    // Commented out becausee not sure if it's needed anywhere.
-                    // $this->item['custom_fields'][$customField->db_column_name()] = '';
+                    // Clear out previous data.
+                    $this->item['custom_fields'][$customField->db_column_name()] = null;
                 }
             }
         }
@@ -106,6 +105,7 @@ class AssetImporter extends ItemImporter
                 $asset->{$custom_field} = $val;
             }
         }
+
         //FIXME: this disables model validation.  Need to find a way to avoid double-logs without breaking everything.
         // $asset->unsetEventDispatcher();
         if ($asset->save()) {
diff --git a/app/Importer/Importer.php b/app/Importer/Importer.php
index 56a6a47eee..45f7d1d170 100644
--- a/app/Importer/Importer.php
+++ b/app/Importer/Importer.php
@@ -116,6 +116,14 @@ abstract class Importer
             $nameLookup[$field['name']] = $field;
             return $nameLookup;
         });
+        // Remove any custom fields that do not exist in the header row.  This prevents nulling out values that shouldn't exist.
+        // In detail, we compare the lower case name of custom fields (indexed by name) to the keys in the header row.  This
+        // results in an array with only custom fields that are in the file.
+        $this->customFields = array_intersect_key(
+            array_change_key_case($this->customFields),
+            array_change_key_case(array_flip($headerRow))
+        );
+
 
         DB::transaction(function () use (&$results) {
             Model::unguard();
diff --git a/tests/unit/ImporterTest.php b/tests/unit/ImporterTest.php
index 03b40f3aa3..7a2803f33e 100644
--- a/tests/unit/ImporterTest.php
+++ b/tests/unit/ImporterTest.php
@@ -88,6 +88,7 @@ EOT;
 
         $this->initializeCustomFields();
         $this->import(new AssetImporter($csv));
+
         $updatedCSV = <<<'EOT'
 item Name,Category,Model name,Manufacturer,Model Number,Serial,Asset Tag,Location,Notes,Purchase Date,Purchase Cost,Company,Status,Warranty,Supplier
 A new name,some other category,Another Model,Linkbridge 32,356,67433477,970882174-8,New Location,I have no notes,2018-04-05,25.59,Another Company,Ready To Go,18,Not Creative