diff --git a/mobile/android/components/SessionStore.js b/mobile/android/components/SessionStore.js
index 9b7f6653cbe..c8ac3116812 100644
--- a/mobile/android/components/SessionStore.js
+++ b/mobile/android/components/SessionStore.js
@@ -939,7 +939,7 @@ SessionStore.prototype = {
 
         // Read session state file into a string and let observers modify the state before it's being used
         let state = Cc["@mozilla.org/supports-string;1"].createInstance(Ci.nsISupportsString);
-        state.data = NetUtil.readInputStreamToString(aStream, aStream.available()) || "";
+        state.data = NetUtil.readInputStreamToString(aStream, aStream.available(), { charset : "UTF-8" }) || "";
         aStream.close();
 
         Services.obs.notifyObservers(state, "sessionstore-state-read", "");
diff --git a/mobile/xul/components/SessionStore.js b/mobile/xul/components/SessionStore.js
index 0d9c7438666..22f51a350ab 100644
--- a/mobile/xul/components/SessionStore.js
+++ b/mobile/xul/components/SessionStore.js
@@ -731,7 +731,7 @@ SessionStore.prototype = {
 
         // Read session state file into a string and let observers modify the state before it's being used
         let state = Cc["@mozilla.org/supports-string;1"].createInstance(Ci.nsISupportsString);
-        state.data = NetUtil.readInputStreamToString(aStream, aStream.available()) || "";
+        state.data = NetUtil.readInputStreamToString(aStream, aStream.available(), { charset : "UTF-8" }) || "";
         aStream.close();
 
         Services.obs.notifyObservers(state, "sessionstore-state-read", "");