diff --git a/plugins/FeedsProcessor.inc b/plugins/FeedsProcessor.inc
index 80e54d5..932f2fe 100755
--- a/plugins/FeedsProcessor.inc
+++ b/plugins/FeedsProcessor.inc
@@ -406,17 +406,6 @@ abstract class FeedsProcessor extends FeedsPlugin {
       $target_item = array();
     }
 
-    // Many mappers add to existing fields rather than replacing them. Hence we
-    // need to clear target elements of each item before mapping in case we are
-    // mapping on a prepopulated item such as an existing node.
-    foreach ($this->config['mappings'] as $mapping) {
-      if (isset($targets[$this->id][$mapping['target']]['real_target'])) {
-        unset($target_item->{$targets[$this->id][$mapping['target']]['real_target']});
-      }
-      elseif (isset($target_item->{$mapping['target']})) {
-        unset($target_item->{$mapping['target']});
-      }
-    }
 
     /*
     This is where the actual mapping happens: For every mapping we envoke
@@ -441,16 +430,29 @@ abstract class FeedsProcessor extends FeedsPlugin {
         $value = $parser->getSourceElement($source, $result, $mapping['source']);
       }
 
-      // Map the source element's value to the target.
-      if (isset($targets[$this->id][$mapping['target']]) &&
-          is_array($targets[$this->id][$mapping['target']]) &&
-          isset($targets[$this->id][$mapping['target']]['callback']) &&
-          function_exists($targets[$this->id][$mapping['target']]['callback'])) {
-        $callback = $targets[$this->id][$mapping['target']]['callback'];
-        $callback($source, $target_item, $mapping['target'], $value, $mapping);
-      }
-      else {
-        $this->setTargetElement($source, $target_item, $mapping['target'], $value, $mapping);
+       if (!empty($value)) {
+        // Many mappers add to existing fields rather than replacing them. Hence we
+        // need to clear target elements of each item before mapping in case we are
+        // mapping on a prepopulated item such as an existing node.
+        // But we do this only for provided mappers, so $value was checked first.
+        if (isset($targets[$mapping['target']]['real_target'])) {
+          unset($target_item->{$targets[$mapping['target']]['real_target']});
+        }
+        elseif (isset($target_item->{$mapping['target']})) {
+          unset($target_item->{$mapping['target']});
+        }
+
+        // Map the source element's value to the target.
+        if (isset($targets[$this->id][$mapping['target']]) &&
+            is_array($targets[$this->id][$mapping['target']]) &&
+            isset($targets[$this->id][$mapping['target']]['callback']) &&
+            function_exists($targets[$this->id][$mapping['target']]['callback'])) {
+          $callback = $targets[$this->id][$mapping['target']]['callback'];
+          $callback($source, $target_item, $mapping['target'], $value);
+        }
+        else {
+          $this->setTargetElement($source, $target_item, $mapping['target'], $value);
+        }
       }
     }
     return $target_item;