--- a/toolkit/modules/UpdateUtils.jsm
+++ b/toolkit/modules/UpdateUtils.jsm
@@ -182,16 +182,24 @@ XPCOMUtils.defineLazyGetter(this, "gSyst
       Cu.reportError("Error getting processor instruction set. " +
                      "Exception: " + e);
     }
 
     lib.close();
     return instructionSet;
   }
 
+  if (AppConstants == "linux") {
+    let instructionSet = "unknown";
+    if navigator.cpuHasSSE2 {
+      instructionSet = "SSE2";
+    }
+    return instructionSet;
+  }
+
   return "NA"
 });
 
 /* Windows only getter that returns the processor architecture. */
 XPCOMUtils.defineLazyGetter(this, "gWinCPUArch", function aus_gWinCPUArch() {
   // Get processor architecture
   let arch = "unknown";