diff --git a/libqpdf/QPDF_linearization.cc b/libqpdf/QPDF_linearization.cc
index 222879e..e4ea689 100644
--- a/libqpdf/QPDF_linearization.cc
+++ b/libqpdf/QPDF_linearization.cc
@@ -130,18 +130,17 @@ QPDF::isLinearized()
             return false;
         }
 
-        QPDFObjectHandle L = candidate.getKey("/L");
-        if (L.isInteger()) {
-            qpdf_offset_t Li = L.getIntValue();
-            m->file->seek(0, SEEK_END);
-            if (Li != m->file->tell()) {
-                QTC::TC("qpdf", "QPDF /L mismatch");
-                return false;
-            } else {
-                m->linp.file_size = Li;
-            }
+        auto L = candidate.getKey("/L");
+        if (!L.isInteger()) {
+            return false;
         }
-
+        qpdf_offset_t Li = L.getIntValue();
+        m->file->seek(0, SEEK_END);
+        if (Li != m->file->tell()) {
+            QTC::TC("qpdf", "QPDF /L mismatch");
+            return false;
+        }
+        m->linp.file_size = Li;
         m->lindict = candidate;
         return true;
     }
diff --git a/manual/release-notes.rst b/manual/release-notes.rst
index 763b1a0..7eae202 100644
--- a/manual/release-notes.rst
+++ b/manual/release-notes.rst
@@ -13,12 +13,20 @@ more detail.
 
 .. x.y.z: not yet released
 
+12.0.1: not yet released
+  - Bug fixes
+
+    - In ``QPDF::isLinearized`` return false if the first object in the file is
+      not a linearization parameter dictionary or its ``/L`` entry is not an
+      integer object. Previously the method returned false if the first
+      dictionary object was not a linearization parameter dictionary.
+
 .. _r12-0-0:
 
 .. cSpell:ignore substract
 
 12.0.0: March 9, 2025
-  - API: breaking changes
+  - API breaking changes
 
     - The header file ``qpdf/QPDFObject.hh`` now generates an error if
       included. This is to prevent code that includes it from