diff --git a/src/items/ean/ean.service.ts b/src/items/ean/ean.service.ts
index e0600e9..2bb5b42 100644
--- a/src/items/ean/ean.service.ts
+++ b/src/items/ean/ean.service.ts
@@ -18,10 +18,14 @@ export class EANService {
   }
 
   isValid(ean: string) {
+    ean = ean.trim();
+    assert(/^\d{13}$/.test(ean));
     return this.calcChecksum(ean.slice(0, 12)) === parseInt(ean[12], 10);
   }
 
   toID(ean: string) {
+    ean = ean.trim();
+    assert(/^\d{12,13}$/.test(ean));
     if (ean.length === 12) {
       // it already is an ID
       return ean;
@@ -33,7 +37,8 @@ export class EANService {
   }
 
   fromID(id: string) {
-    assert(id.length === 12);
+    id = id.trim();
+    assert(/^\d{12}$/.test(id));
     return id + this.calcChecksum(id);
   }
 }