diff --git a/lib/utils/validation-utils.js b/lib/utils/validation-utils.js
--- a/lib/utils/validation-utils.js
+++ b/lib/utils/validation-utils.js
@@ -24,19 +24,19 @@
   VideoMessageServerDBContent,
 } from '../types/messages/media';
 
-function tBool(value: boolean): TIrreducible<boolean> {
+function tBool<T: boolean>(value: T): TIrreducible<T> {
   return t.irreducible(value.toString(), x => x === value);
 }
 
-function tString(value: string): TIrreducible<string> {
+function tString<T: string>(value: T): TIrreducible<T> {
   return t.irreducible(`'${value}'`, x => x === value);
 }
 
-function tNumber(value: number): TIrreducible<number> {
+function tNumber<T: number>(value: T): TIrreducible<T> {
   return t.irreducible(value.toString(), x => x === value);
 }
 
-function tShape<T>(spec: TStructProps<T>): TInterface<T> {
+function tShape<T: { +[string]: mixed }>(spec: TStructProps<T>): TInterface<T> {
   return t.interface(spec, { strict: true });
 }