diff --git a/src/types/routeMethods.ts b/src/types/routeMethods.ts
index a571982b..e70c80f2 100644
--- a/src/types/routeMethods.ts
+++ b/src/types/routeMethods.ts
@@ -124,7 +124,7 @@ type ExtractPathParamType<
     ? ExtractParamType<TParams[TParam]>
     : string
 
-type ExtractParamType<TParam extends Param | undefined> = TParam extends ParamGetSet<infer Type>
+export type ExtractParamType<TParam extends Param | undefined> = TParam extends ParamGetSet<infer Type>
   ? Type
   : TParam extends ParamGetter
     ? ReturnType<TParam>
diff --git a/src/utilities/params.ts b/src/utilities/params.ts
index 599b2b94..e1a41156 100644
--- a/src/utilities/params.ts
+++ b/src/utilities/params.ts
@@ -1,4 +1,4 @@
-import { Param, ParamGetSet, ParamExtras, isParamGetSet, isParamGetter } from '@/types'
+import { Param, ParamGetSet, ParamExtras, isParamGetSet, isParamGetter, ExtractParamType } from '@/types'
 import { InvalidRouteParamValueError } from '@/types/invalidRouteParamValueError'
 
 const extras: ParamExtras = {
@@ -7,7 +7,7 @@ const extras: ParamExtras = {
   },
 }
 
-const booleanParam: ParamGetSet = {
+const booleanParam: ParamGetSet<unknown> = {
   get: (value, { invalid }) => {
     if (value === 'true') {
       return true
@@ -28,7 +28,7 @@ const booleanParam: ParamGetSet = {
   },
 }
 
-const numberParam: ParamGetSet = {
+const numberParam: ParamGetSet<unknown> = {
   get: (value, { invalid }) => {
     // Number('') === 0
     if (value.length === 0) {
@@ -45,14 +45,15 @@ const numberParam: ParamGetSet = {
   },
   set: (value, { invalid }) => {
     if (typeof value !== 'number') {
-      invalid()
+      throw invalid()
     }
 
     return value.toString()
   },
 }
 
-export function getParamValue(value: string, param: Param): unknown {
+export function getParamValue<T extends Param>(value: string, param: T): ExtractParamType<T>
+export function getParamValue<T extends Param>(value: string, param: T): unknown {
   if (param === Boolean) {
     return booleanParam.get(value, extras)
   }