diff --git a/package-lock.json b/package-lock.json
index 60b6e9f31..ef4ab7efc 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -77,6 +77,8 @@
         "@types/google.maps": "^3.58.1",
         "@types/leaflet": "^1.9.16",
         "@types/node": "^20.17.22",
+        "@types/proj4": "^2.5.6",
+        "@types/proj4leaflet": "^1.0.10",
         "@types/react-dom": "^18.3.5",
         "@typescript-eslint/parser": "^8.19.0",
         "@utrecht/component-library-css": "1.0.0-alpha.604",
@@ -5988,6 +5990,23 @@
       "resolved": "https://registry.npmjs.org/@types/parse-json/-/parse-json-4.0.2.tgz",
       "integrity": "sha512-dISoDXWWQwUquiKsyZ4Ng+HX2KsPL7LyHKHQwgGFEA3IaKac4Obd+h2a/a6waisAoepJlBcx9paWqjA8/HVjCw=="
     },
+    "node_modules/@types/proj4": {
+      "version": "2.5.6",
+      "resolved": "https://registry.npmjs.org/@types/proj4/-/proj4-2.5.6.tgz",
+      "integrity": "sha512-zfMrPy9fx+8DchqM0kIUGeu2tTVB5ApO1KGAYcSGFS8GoqRIkyL41xq2yCx/iV3sOLzo7v4hEgViSLTiPI1L0w==",
+      "dev": true
+    },
+    "node_modules/@types/proj4leaflet": {
+      "version": "1.0.10",
+      "resolved": "https://registry.npmjs.org/@types/proj4leaflet/-/proj4leaflet-1.0.10.tgz",
+      "integrity": "sha512-Yie5J8sHUgTQ1FTRP9cCDXpWvHXjUiSjwlnJb1F06Czwo6cVOt8Bxy6txMSIVgznbnRWlbYmxNjWDhYtNxAflw==",
+      "dev": true,
+      "dependencies": {
+        "@types/geojson": "*",
+        "@types/leaflet": "*",
+        "@types/proj4": "*"
+      }
+    },
     "node_modules/@types/prop-types": {
       "version": "15.7.11",
       "resolved": "https://registry.npmjs.org/@types/prop-types/-/prop-types-15.7.11.tgz",
diff --git a/package.json b/package.json
index b3335beb6..732bbfc38 100644
--- a/package.json
+++ b/package.json
@@ -126,6 +126,8 @@
     "@types/google.maps": "^3.58.1",
     "@types/leaflet": "^1.9.16",
     "@types/node": "^20.17.22",
+    "@types/proj4": "^2.5.6",
+    "@types/proj4leaflet": "^1.0.10",
     "@types/react-dom": "^18.3.5",
     "@typescript-eslint/parser": "^8.19.0",
     "@utrecht/component-library-css": "1.0.0-alpha.604",