diff --git a/requirements.in b/requirements.in
index 3dca6e7..0473e1f 100644
--- a/requirements.in
+++ b/requirements.in
@@ -6,3 +6,4 @@ rtree
 pillow
 requests
 pyproj
+scikit-fmm
diff --git a/requirements.txt b/requirements.txt
index 00f5e20..4f70344 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -15,7 +15,9 @@ cython==3.0.8
 idna==2.10
     # via requests
 numpy==1.23.5
-    # via -r requirements.in
+    # via
+    #   -r requirements.in
+    #   scikit-fmm
 pillow==10.2.0
     # via -r requirements.in
 pyproj==3.4.1
@@ -24,6 +26,8 @@ requests==2.31.0
     # via -r requirements.in
 rtree==0.9.7
     # via -r requirements.in
+scikit-fmm==2023.4.2
+    # via -r requirements.in
 shapely==1.8.5
     # via -r requirements.in
 urllib3==1.26.18