diff --git a/src/Spout/Writer/ODS/Manager/WorksheetManager.php b/src/Spout/Writer/ODS/Manager/WorksheetManager.php
index 7d7cb0e..bd87dc1 100644
--- a/src/Spout/Writer/ODS/Manager/WorksheetManager.php
+++ b/src/Spout/Writer/ODS/Manager/WorksheetManager.php
@@ -243,7 +243,9 @@ class WorksheetManager implements WorksheetManagerInterface
         } elseif ($cell->isEmpty()) {
             $data .= '/>';
         } else {
-            throw new InvalidArgumentException('Trying to add a value with an unsupported type: ' . \gettype($cell->getValue()));
+            $value = $cell->getValue();
+
+            throw new InvalidArgumentException('Trying to add a value with an unsupported type: ' . (\is_object($value) ? \get_class($value) : \gettype($value)));
         }
 
         return $data;
diff --git a/src/Spout/Writer/XLSX/Manager/WorksheetManager.php b/src/Spout/Writer/XLSX/Manager/WorksheetManager.php
index 61b93a1..b67f7ac 100644
--- a/src/Spout/Writer/XLSX/Manager/WorksheetManager.php
+++ b/src/Spout/Writer/XLSX/Manager/WorksheetManager.php
@@ -253,7 +253,9 @@ EOD;
                 $cellXML = '';
             }
         } else {
-            throw new InvalidArgumentException('Trying to add a value with an unsupported type: ' . \gettype($cell->getValue()));
+            $value = $cell->getValue();
+
+            throw new InvalidArgumentException('Trying to add a value with an unsupported type: ' . (\is_object($value) ? \get_class($value) : \gettype($value)));
         }
 
         return $cellXML;