diff --git a/README.md b/README.md
index d8c8184..d6e581f 100644
--- a/README.md
+++ b/README.md
@@ -25,8 +25,9 @@ Python 3.6+ installation. We try to keep the external dependencies at a minimum,
 in order to keep compatibility with different platforms, including Pythonista
 on iOS. At this moment, we require:
 
-  - Pillow>=6.2.2
+  - Pillow>=8.0.1
   - piexif>=1.1.3
+  - watchdog>=0.10.3
 
 The easiest way to install it in a single step, including any dependencies, is 
 by using this command:
diff --git a/changelog.txt b/changelog.txt
index 8182003..e284f84 100755
--- a/changelog.txt
+++ b/changelog.txt
@@ -4,7 +4,7 @@ Version history:
 ================
 
 ---
-v.1.4.0 - 2020-?
+v.1.4.0 - 2020-11-01
  * New feature: watch a directory for changes and optimize any new image file as
    soon as it is created (no multiprocessing for now, sorry). This feature is
    not compatible with Pythonista for iOS, since it requires a third-party
diff --git a/docs/docs_EN.md b/docs/docs_EN.md
index 3b3db2a..7b1f67a 100644
--- a/docs/docs_EN.md
+++ b/docs/docs_EN.md
@@ -52,7 +52,7 @@ Python 3.6+ installation. We try to keep the external dependencies at a minimum,
 in order to keep compatibility with different platforms, including Pythonista
 on iOS. At this moment, we require:
 
-  - Pillow>=8.0.0
+  - Pillow>=8.0.1
   - piexif>=1.1.3
   - watchdog>=0.10.3
 
diff --git a/docs/docs_PT.md b/docs/docs_PT.md
index 556032f..60a0610 100644
--- a/docs/docs_PT.md
+++ b/docs/docs_PT.md
@@ -54,7 +54,7 @@ superior. Procuramos manter no mínimo as dependências externas, de modo a
 manter a compatibilidade com diferentes plataformas, incluindo Pythonista em
 iOS. Neste momento, requer:
 
-  - Pillow>=8.0.0
+  - Pillow>=8.0.1
   - piexif>=1.1.3
   - watchdog>=0.10.3
 
diff --git a/optimize_images/__init__.py b/optimize_images/__init__.py
index 714be0b..96e3ce8 100755
--- a/optimize_images/__init__.py
+++ b/optimize_images/__init__.py
@@ -1 +1 @@
-__version__ = '1.4.0a1'
+__version__ = '1.4.0'
diff --git a/optimize_images/img_dynamic_quality.py b/optimize_images/img_dynamic_quality.py
index b6c3dd9..a895be5 100644
--- a/optimize_images/img_dynamic_quality.py
+++ b/optimize_images/img_dynamic_quality.py
@@ -62,7 +62,7 @@ def get_diff_at_quality(photo, quality):
         return 1 - diff_score / 100
 
 
-@lru_cache
+@lru_cache(maxsize=None)
 def _diff_iteration_count(lo, hi):
     """Return the depth of the binary search tree for this range"""
     if lo >= hi:
diff --git a/optimize_images/platforms.py b/optimize_images/platforms.py
index 6a6ef9e..4e3d9cb 100755
--- a/optimize_images/platforms.py
+++ b/optimize_images/platforms.py
@@ -35,7 +35,7 @@ def __init__(self):
             self.size_is_smaller = 'v'
 
 
-@lru_cache
+@lru_cache(maxsize=None)
 def adjust_for_platform() -> Tuple[int, Union[TPoolExType, PPoolExType], int]:
     if platform.system() == 'Darwin':
         if platform.machine().startswith('iPad'):
diff --git a/optimize_images/reporting.py b/optimize_images/reporting.py
index db96874..08d3301 100644
--- a/optimize_images/reporting.py
+++ b/optimize_images/reporting.py
@@ -5,7 +5,7 @@
 from optimize_images.platforms import IconGenerator
 
 
-@lru_cache
+@lru_cache(maxsize=None)
 def human(number: int, suffix='B') -> str:
     """Return a human readable memory size in a string.
 
diff --git a/requirements_development.txt b/requirements_development.txt
deleted file mode 100644
index 61ef1d1..0000000
--- a/requirements_development.txt
+++ /dev/null
@@ -1,21 +0,0 @@
-bleach==3.1.4
-certifi==2019.6.16
-cffi==1.12.3
-chardet==3.0.4
-cmarkgfm==0.4.2
-docutils==0.14
-future==0.17.1
-idna==2.8
-piexif==1.1.3
-Pillow==6.2.2
-pkginfo==1.5.0.1
-pycparser==2.19
-Pygments==2.4.2
-readme-renderer==24.0
-requests==2.22.0
-requests-toolbelt==0.9.1
-six==1.12.0
-tqdm==4.32.2
-twine==1.13.0
-urllib3==1.25.3
-webencodings==0.5.1
diff --git a/requirements_for_desktop.txt b/requirements_for_desktop.txt
index 5a2c77e..83f7efa 100644
--- a/requirements_for_desktop.txt
+++ b/requirements_for_desktop.txt
@@ -1,3 +1,3 @@
-Pillow>=8.0.0
+Pillow>=8.0.01
 piexif>=1.1.3
 watchdog>=0.10.3
diff --git a/setup.py b/setup.py
index 76622a6..d70a0f9 100644
--- a/setup.py
+++ b/setup.py
@@ -5,7 +5,7 @@
 import platform
 
 used = sys.version_info
-required = (3, 6)
+required = (3, 7)
 
 # if version of pip that doesn't understand the python_requires classifier, must be pip >= 9.0.0
 # must be built using at least version 24.2.0 of setuptools
@@ -40,7 +40,7 @@ def read_readme(file_name):
           'Source': 'https://github.com/victordomingos/optimize-images',
           'Bug Reports': 'https://github.com/victordomingos/optimize-images/issues',
       },
-      python_requires='>=3.6',
+      python_requires='>=3.7',
       classifiers=[
           'Development Status :: 4 - Beta',
           'Environment :: Console',
@@ -55,9 +55,9 @@ def read_readme(file_name):
           'Operating System :: Unix',
           'Operating System :: POSIX :: Linux ',
           'Programming Language :: Python :: 3',
-          'Programming Language :: Python :: 3.6',
           'Programming Language :: Python :: 3.7',
           'Programming Language :: Python :: 3.8',
+          'Programming Language :: Python :: 3.9',
           'Topic :: Utilities',
           'Topic :: Multimedia :: Graphics',
           'Topic :: Multimedia :: Graphics :: Graphics Conversion',
@@ -68,7 +68,7 @@ def read_readme(file_name):
                'seo-optimization website-performance cli recursive non-recursive',
 
       install_requires=[
-          'piexif>=1.1.3',
+          'piexif==1.1.3',
       ],
 
       entry_points={