diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 29bdc49fa0..b267f8c3b3 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -6,30 +6,6 @@ parameters:
 			count: 1
 			path: src/PhpSpreadsheet/Calculation/LookupRef/Sort.php
 
-		-
-			message: '#^Cannot call method getAllSpContainers\(\) on mixed\.$#'
-			identifier: method.nonObject
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xls/LoadSpreadsheet.php
-
-		-
-			message: '#^Cannot call method getBSECollection\(\) on mixed\.$#'
-			identifier: method.nonObject
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xls/LoadSpreadsheet.php
-
-		-
-			message: '#^Cannot call method getBstoreContainer\(\) on mixed\.$#'
-			identifier: method.nonObject
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xls/LoadSpreadsheet.php
-
-		-
-			message: '#^Cannot call method getSpgrContainer\(\) on mixed\.$#'
-			identifier: method.nonObject
-			count: 1
-			path: src/PhpSpreadsheet/Reader/Xls/LoadSpreadsheet.php
-
 		-
 			message: '#^Cannot access offset 0 on mixed\.$#'
 			identifier: offsetAccess.nonOffsetAccessible
diff --git a/src/PhpSpreadsheet/Reader/Xls/Escher.php b/src/PhpSpreadsheet/Reader/Xls/Escher.php
index 094c19e877..018c17189e 100644
--- a/src/PhpSpreadsheet/Reader/Xls/Escher.php
+++ b/src/PhpSpreadsheet/Reader/Xls/Escher.php
@@ -12,6 +12,9 @@
 use PhpOffice\PhpSpreadsheet\Shared\Escher\DggContainer\BstoreContainer\BSE;
 use PhpOffice\PhpSpreadsheet\Shared\Escher\DggContainer\BstoreContainer\BSE\Blip;
 
+/**
+ * @template T of BSE|BstoreContainer|DgContainer|DggContainer|\PhpOffice\PhpSpreadsheet\Shared\Escher|SpContainer|SpgrContainer
+ */
 class Escher
 {
     const DGGCONTAINER = 0xF000;
@@ -50,11 +53,15 @@ class Escher
 
     /**
      * The object to be returned by the reader. Modified during load.
+     *
+     * @var T
      */
     private BSE|BstoreContainer|DgContainer|DggContainer|\PhpOffice\PhpSpreadsheet\Shared\Escher|SpContainer|SpgrContainer $object;
 
     /**
      * Create a new Escher instance.
+     *
+     * @param T $object
      */
     public function __construct(BSE|BstoreContainer|DgContainer|DggContainer|\PhpOffice\PhpSpreadsheet\Shared\Escher|SpContainer|SpgrContainer $object)
     {
@@ -84,6 +91,8 @@ public function __construct(BSE|BstoreContainer|DgContainer|DggContainer|\PhpOff
 
     /**
      * Load Escher stream data. May be a partial Escher stream.
+     *
+     * @return T
      */
     public function load(string $data): BSE|BstoreContainer|DgContainer|DggContainer|\PhpOffice\PhpSpreadsheet\Shared\Escher|SpContainer|SpgrContainer
     {
diff --git a/src/PhpSpreadsheet/Reader/Xls/LoadSpreadsheet.php b/src/PhpSpreadsheet/Reader/Xls/LoadSpreadsheet.php
index 76e4235b8e..5c27b0cc3d 100644
--- a/src/PhpSpreadsheet/Reader/Xls/LoadSpreadsheet.php
+++ b/src/PhpSpreadsheet/Reader/Xls/LoadSpreadsheet.php
@@ -435,7 +435,7 @@ protected function loadSpreadsheetFromFile2(string $filename, Xls $xls): Spreads
 
                 // get all spContainers in one long array, so they can be mapped to OBJ records
                 /** @var SpContainer[] $allSpContainers */
-                $allSpContainers = method_exists($escherWorksheet, 'getDgContainer') ? $escherWorksheet->getDgContainer()->getSpgrContainer()->getAllSpContainers() : [];
+                $allSpContainers = $escherWorksheet->getDgContainerOrThrow()->getSpgrContainerOrThrow()->getAllSpContainers();
             }
 
             // treat OBJ records
@@ -497,7 +497,7 @@ protected function loadSpreadsheetFromFile2(string $filename, Xls $xls): Spreads
 
                             if ($escherWorkbook) {
                                 /** @var BSE[] */
-                                $BSECollection = method_exists($escherWorkbook, 'getDggContainer') ? $escherWorkbook->getDggContainer()->getBstoreContainer()->getBSECollection() : [];
+                                $BSECollection = $escherWorkbook->getDggContainerOrThrow()->getBstoreContainerOrThrow()->getBSECollection();
                                 $BSE = $BSECollection[$BSEindex - 1];
                                 $blipType = $BSE->getBlipType();
 
diff --git a/src/PhpSpreadsheet/Shared/Escher.php b/src/PhpSpreadsheet/Shared/Escher.php
index 9eb9956a2f..00180f6e25 100644
--- a/src/PhpSpreadsheet/Shared/Escher.php
+++ b/src/PhpSpreadsheet/Shared/Escher.php
@@ -2,6 +2,8 @@
 
 namespace PhpOffice\PhpSpreadsheet\Shared;
 
+use PhpOffice\PhpSpreadsheet\Exception as SpreadsheetException;
+
 class Escher
 {
     /**
@@ -22,6 +24,14 @@ public function getDggContainer(): ?Escher\DggContainer
         return $this->dggContainer;
     }
 
+    /**
+     * Get Drawing Group Container.
+     */
+    public function getDggContainerOrThrow(): Escher\DggContainer
+    {
+        return $this->dggContainer ?? throw new SpreadsheetException('dggContainer is unexpectedly null');
+    }
+
     /**
      * Set Drawing Group Container.
      */
@@ -38,6 +48,14 @@ public function getDgContainer(): ?Escher\DgContainer
         return $this->dgContainer;
     }
 
+    /**
+     * Get Drawing Container.
+     */
+    public function getDgContainerOrThrow(): Escher\DgContainer
+    {
+        return $this->dgContainer ?? throw new SpreadsheetException('dgContainer is unexpectedly null');
+    }
+
     /**
      * Set Drawing Container.
      */
diff --git a/src/PhpSpreadsheet/Shared/Escher/DggContainer.php b/src/PhpSpreadsheet/Shared/Escher/DggContainer.php
index eb8829c0cb..e5d831fa77 100644
--- a/src/PhpSpreadsheet/Shared/Escher/DggContainer.php
+++ b/src/PhpSpreadsheet/Shared/Escher/DggContainer.php
@@ -2,6 +2,8 @@
 
 namespace PhpOffice\PhpSpreadsheet\Shared\Escher;
 
+use PhpOffice\PhpSpreadsheet\Exception as SpreadsheetException;
+
 class DggContainer
 {
     /**
@@ -94,6 +96,14 @@ public function getBstoreContainer(): ?DggContainer\BstoreContainer
         return $this->bstoreContainer;
     }
 
+    /**
+     * Get BLIP Store Container.
+     */
+    public function getBstoreContainerOrThrow(): DggContainer\BstoreContainer
+    {
+        return $this->bstoreContainer ?? throw new SpreadsheetException('bstoreContainer is unexpectedly null');
+    }
+
     /**
      * Set BLIP Store Container.
      */