diff --git a/.ops/aws-setup/package.json b/.ops/aws-setup/package.json
index 7b7b9db972..5e2a2f3f1f 100644
--- a/.ops/aws-setup/package.json
+++ b/.ops/aws-setup/package.json
@@ -36,6 +36,7 @@
             "prettier"
         ],
         "rules": {
+            "prefer-const": "error",
             "prettier/prettier": "error",
             "no-unused-vars": [
                 "error",
diff --git a/e2e/package.json b/e2e/package.json
index 991c6f6e76..707578ffe6 100644
--- a/e2e/package.json
+++ b/e2e/package.json
@@ -30,6 +30,7 @@
       "plugin:prettier/recommended"
     ],
     "rules": {
+      "prefer-const": "error",
       "prettier/prettier": "error"
     }
   }
diff --git a/e2e/specs/nuxtPrint.cy.js b/e2e/specs/nuxtPrint.cy.js
index 99f450b7bf..e9938c0b04 100644
--- a/e2e/specs/nuxtPrint.cy.js
+++ b/e2e/specs/nuxtPrint.cy.js
@@ -11,7 +11,7 @@ describe('Nuxt print test', () => {
       const campUri = body._links.items[1].href
       const camp = body._embedded.items[1]
 
-      let printConfig = {
+      const printConfig = {
         language: 'en',
         documentName: 'camp',
         camp: campUri,
diff --git a/frontend/package.json b/frontend/package.json
index 033da40bf7..b9fb201f5e 100644
--- a/frontend/package.json
+++ b/frontend/package.json
@@ -130,6 +130,7 @@
       "@vue/eslint-config-prettier"
     ],
     "rules": {
+      "prefer-const": "error",
       "prettier/prettier": "error",
       "vue/component-tags-order": [
         "error",
diff --git a/frontend/src/components/campAdmin/DialogPeriodDateEdit.vue b/frontend/src/components/campAdmin/DialogPeriodDateEdit.vue
index 18dd362601..d725df35c7 100644
--- a/frontend/src/components/campAdmin/DialogPeriodDateEdit.vue
+++ b/frontend/src/components/campAdmin/DialogPeriodDateEdit.vue
@@ -118,8 +118,8 @@ export default {
       return this.$date.utc(this.entityData.end, 'YYYY-MM-DD').format('L')
     },
     periodDurationInDays() {
-      let start = this.$date.utc(this.entityData.start, 'YYYY-MM-DD')
-      let end = this.$date.utc(this.entityData.end, 'YYYY-MM-DD')
+      const start = this.$date.utc(this.entityData.start, 'YYYY-MM-DD')
+      const end = this.$date.utc(this.entityData.end, 'YYYY-MM-DD')
       return 1 + end.diff(start, 'day')
     },
   },
@@ -139,11 +139,11 @@ export default {
   methods: {
     startChanged() {
       if (this.mode == 'move') {
-        let origStart = this.$date.utc(this.period.start, 'YYYY-MM-DD')
-        let origEnd = this.$date.utc(this.period.end, 'YYYY-MM-DD')
-        let origLength = origEnd - origStart
-        let start = this.$date.utc(this.entityData.start, 'YYYY-MM-DD')
-        let end = start.add(origLength)
+        const origStart = this.$date.utc(this.period.start, 'YYYY-MM-DD')
+        const origEnd = this.$date.utc(this.period.end, 'YYYY-MM-DD')
+        const origLength = origEnd - origStart
+        const start = this.$date.utc(this.entityData.start, 'YYYY-MM-DD')
+        const end = start.add(origLength)
         this.entityData.end = end.format('YYYY-MM-DD')
       }
     },
diff --git a/frontend/src/components/program/FormScheduleEntryItem.vue b/frontend/src/components/program/FormScheduleEntryItem.vue
index 24fe5c35f3..36afabbb47 100644
--- a/frontend/src/components/program/FormScheduleEntryItem.vue
+++ b/frontend/src/components/program/FormScheduleEntryItem.vue
@@ -111,7 +111,7 @@ export default {
         .isSame(this.$date.utc(this.localScheduleEntry.end), 'day')
     },
     endTimeValidation() {
-      let validator = {
+      const validator = {
         required: true,
       }
 
diff --git a/pdf/package.json b/pdf/package.json
index f6724b5df7..8cb9c4368e 100644
--- a/pdf/package.json
+++ b/pdf/package.json
@@ -67,6 +67,7 @@
       "@vue/eslint-config-prettier"
     ],
     "rules": {
+      "prefer-const": "error",
       "prettier/prettier": "error",
       "vue/component-tags-order": [
         "error",
diff --git a/print/package.json b/print/package.json
index adf7c92fcc..5f99a6f006 100644
--- a/print/package.json
+++ b/print/package.json
@@ -70,6 +70,7 @@
       "no-undef": "off",
       "no-console": "off",
       "prettier/prettier": "error",
+      "prefer-const": "error",
       "vue/multi-word-component-names": "off",
       "local-rules/matching-translation-keys": [
         "error",