diff --git a/CHANGELOG.md b/CHANGELOG.md
index f51e422e02..aae973d8ed 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 0.18.27-dev5
+
+### Enhancement
+- Upgrade pdfminer-six to 20260107 to fix ~15-18% performance regression from eager f-string evaluation
+
 ## 0.18.27-dev4
 
 ### Fixes
diff --git a/requirements/extra-pdf-image.txt b/requirements/extra-pdf-image.txt
index 1ccfed216d..047a52cde2 100644
--- a/requirements/extra-pdf-image.txt
+++ b/requirements/extra-pdf-image.txt
@@ -146,7 +146,7 @@ pandas==2.3.3
     # via unstructured-inference
 pdf2image==1.17.0
     # via -r extra-pdf-image.in
-pdfminer-six==20251230
+pdfminer-six==20260107
     # via
     #   -r extra-pdf-image.in
     #   unstructured-inference
diff --git a/unstructured/__version__.py b/unstructured/__version__.py
index cd393308d2..c72d9a6020 100644
--- a/unstructured/__version__.py
+++ b/unstructured/__version__.py
@@ -1 +1 @@
-__version__ = "0.18.27-dev4"  # pragma: no cover
+__version__ = "0.18.27-dev5"  # pragma: no cover