diff --git a/pyproject.toml b/pyproject.toml
index 7b8e336..45602a6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -18,7 +18,8 @@ authors = [
 requires-python = ">=3.9"
 dependencies = [
     "PyYAML",
-    "tqdm"
+    "tqdm",
+    "dill"
 ]
 
 [project.optional-dependencies]
diff --git a/requirements-demos.txt b/requirements-demos.txt
index a54d6e2..af0692a 100644
--- a/requirements-demos.txt
+++ b/requirements-demos.txt
@@ -27,6 +27,8 @@ contourpy==1.1.1
     # via matplotlib
 cycler==0.12.1
     # via matplotlib
+dill==0.3.7
+    # via WSIMOD (pyproject.toml)
 fiona==1.9.5
     # via geopandas
 fonttools==4.43.1
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 389b4fd..f78b3b1 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -8,6 +8,8 @@ colorama==0.4.6
     # via
     #   pytest
     #   tqdm
+dill==0.3.7
+    # via WSIMOD (pyproject.toml)
 iniconfig==2.0.0
     # via pytest
 packaging==23.2
diff --git a/requirements-doc.txt b/requirements-doc.txt
index efbf41e..b9f5bb6 100644
--- a/requirements-doc.txt
+++ b/requirements-doc.txt
@@ -38,6 +38,8 @@ decorator==5.1.1
     # via ipython
 defusedxml==0.7.1
     # via nbconvert
+dill==0.3.7
+    # via WSIMOD (pyproject.toml)
 executing==2.0.1
     # via stack-data
 fastjsonschema==2.18.1
diff --git a/requirements.txt b/requirements.txt
index be4cbba..1b54f7a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,6 +6,8 @@
 #
 colorama==0.4.6
     # via tqdm
+dill==0.3.7
+    # via WSIMOD (pyproject.toml)
 pyyaml==6.0.1
     # via WSIMOD (pyproject.toml)
 tqdm==4.66.1