diff --git a/requirements-docs.txt b/requirements-docs.txt
index 9057a2a..d5f1ee5 100644
--- a/requirements-docs.txt
+++ b/requirements-docs.txt
@@ -1,2 +1,2 @@
-Sphinx==1.7.1
-sphinx_rtd_theme==0.2.5b2
+Sphinx<7
+sphinx_rtd_theme<2
diff --git a/requirements-release.txt b/requirements-release.txt
index 2a065e6..17275d8 100644
--- a/requirements-release.txt
+++ b/requirements-release.txt
@@ -1,3 +1,4 @@
-bumpversion==0.5.3
-twine==1.11.0
-keyring==11.1.0
+build
+bump2version>=1,<2
+keyring>=20,<24
+twine>=3,<5
diff --git a/setup.py b/setup.py
index e365040..62fb1e7 100644
--- a/setup.py
+++ b/setup.py
@@ -1,5 +1,4 @@
 import os
-import sys
 from setuptools import setup, find_packages
 
 here = os.path.abspath(os.path.dirname(__file__))
@@ -7,17 +6,17 @@
 CHANGES = open(os.path.join(here, 'CHANGES.rst')).read()
 
 requires = [
-    'pandas>=0.23.4',
-    'requests>=2.18.4',
-    'requests-ftp>=0.3.1',
-    'docopt>=0.6.2',
+    'appdirs>=1.4.3,<2',
+    'arrow>=0.12.1,<0.18',  # Verified to work on 0.17.0.
     'attrs>=17.4.0',
-    'tabulate>=0.8.2',
-    'dogpile.cache>=0.6.5',
-    'arrow>=0.12.1',
-    'tqdm>=4.19.7',
-    'appdirs>=1.4.3',
+    'docopt>=0.6.2',
+    'dogpile.cache>=0.6.5,<1',  # Verified to work on 1.1.1.
     'future',
+    'pandas>=0.23.4,<1.3',  # Verified to work on 1.2.0.
+    'requests>=2.18.4,<3',
+    'requests-ftp>=0.3.1,<4',  # Verified to work on 0.3.1.
+    'tabulate>=0.8.2,<0.9',  # Verified to work on 0.8.7.
+    'tqdm>=4,<5',
 ]
 
 test_requires = [
@@ -27,11 +26,16 @@
     version='0.11.0',
     description='phenodata is a data acquisition and manipulation toolkit for open access phenology data',
     long_description=README,
-    license="AGPL 3",
+    license="AGPL 3, EUPL 1.2",
     classifiers=[
         "Programming Language :: Python",
-        "Programming Language :: Python :: 2",
         "Programming Language :: Python :: 3",
+        "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
+        "Programming Language :: Python :: 3.10",
+        "Programming Language :: Python :: 3.11",
         "Development Status :: 4 - Beta",
         "Environment :: Console",
         "Environment :: Web Environment",
@@ -40,6 +44,7 @@
         "Intended Audience :: End Users/Desktop",
         "Intended Audience :: Information Technology",
         "Intended Audience :: Science/Research",
+        "License :: OSI Approved :: European Union Public Licence 1.2 (EUPL 1.2)",
         "License :: OSI Approved :: GNU Affero General Public License v3",
         "Natural Language :: English",
         "Natural Language :: German",
@@ -76,7 +81,7 @@
     install_requires=requires,
     tests_require=test_requires,
     extras_require={
-        'sql': ['duckdb']
+        'sql': ['duckdb<0.7']
     },
     dependency_links=[
     ],