diff --git a/src/ssn/getPatch.ts b/src/ssn/getPatch.ts
index ef7054d..c05ef4a 100644
--- a/src/ssn/getPatch.ts
+++ b/src/ssn/getPatch.ts
@@ -14,7 +14,13 @@ export default async function getPatch(product: Product, from: number, to: numbe
 
   const fileEntries = readSsnFile(zipFile);
 
-  //TODO: verify file entries
+  //Verify file entries
+  if (from === -1) {
+    fileEntries.filter((file) => file.diffType !== SsnDiffType.NewFile).forEach((file) => {
+      throw new Error(`Patches from -1 must be included in full, but this patch had a file "${file.name}" with diff type ${file.diffType}.`);
+    });
+  }
+  //TODO: last file must always be `${product}.version` with diff type. Other files depend on diffType.
   console.log(fileEntries);
 
   //Extract newly added files