diff --git a/test/general/streaming.js b/test/general/streaming.js
index 6bc1e104..5692bb34 100644
--- a/test/general/streaming.js
+++ b/test/general/streaming.js
@@ -239,6 +239,7 @@ function tests() {
 
       const msgAsciiArmored = encrypted.data;
       const message = await openpgp.message.readArmored(openpgp.stream.transform(msgAsciiArmored, value => {
+        value += '';
         if (value === '\n=' || value.length === 4) return; // Remove checksum
         if (value.length > 1000) return value.slice(0, 499) + (value[499] === 'a' ? 'b' : 'a') + value.slice(500);
         return value;
@@ -276,6 +277,7 @@ function tests() {
 
       const msgAsciiArmored = encrypted.data;
       const message = await openpgp.message.readArmored(openpgp.stream.transform(msgAsciiArmored, value => {
+        value += '';
         if (value.length > 1000) return value.slice(0, 499) + (value[499] === 'a' ? 'b' : 'a') + value.slice(500);
         return value;
       }));
@@ -313,6 +315,7 @@ function tests() {
 
       const msgAsciiArmored = encrypted.data;
       const message = await openpgp.message.readArmored(openpgp.stream.transform(msgAsciiArmored, value => {
+        value += '';
         if (value.length > 1000) return value.slice(0, 499) + (value[499] === 'a' ? 'b' : 'a') + value.slice(500);
         return value;
       }));
@@ -349,6 +352,7 @@ function tests() {
 
       const msgAsciiArmored = signed.data;
       const message = await openpgp.message.readArmored(openpgp.stream.transform(msgAsciiArmored, value => {
+        value += '';
         if (value.length > 1000) return value.slice(0, 499) + (value[499] === 'a' ? 'b' : 'a') + value.slice(500);
         return value;
       }));