diff --git a/toolkit/components/places/UnifiedComplete.js b/toolkit/components/places/UnifiedComplete.js
--- a/toolkit/components/places/UnifiedComplete.js
+++ b/toolkit/components/places/UnifiedComplete.js
@@ -506,11 +506,13 @@
  */
 function looksLikeUrl(str, ignoreAlphanumericHosts = false) {
   // Single word including special chars.
   return !REGEXP_SPACES.test(str) &&
          (["/", "@", ":", "["].some(c => str.includes(c)) ||
-          (ignoreAlphanumericHosts ? /(.*\..*){3,}/.test(str) : str.includes(".")));
+          (ignoreAlphanumericHosts ?
+            /^([\[\]A-Z0-9.:-]+[\.:]){3,}[\[\]A-Z0-9.:-]+$/i.test(str) :
+            str.includes(".")));
 }
 
 /**
  * Returns whether the passed in string looks like an origin.
  */