diff --git a/app/models/user.rb b/app/models/user.rb
index c6fed18bb..8a76b6e40 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -23,7 +23,7 @@ class User < ApplicationRecord
   validates :username,
     presence: true,
     uniqueness: {case_sensitive: false},
-    format: {with: /\A[[:alnum:]]{3,}\z/}
+    format: {with: /\A[[:alnum:]]+\z/}
 
   validates :email,
     presence: true,
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index 5a1e7014f..dc1641535 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -8,12 +8,12 @@
     expect(build(:user, username: nil)).not_to be_valid
   end
 
-  it "doesn't allow single-character usernames" do
-    expect(build(:user, username: "a")).not_to be_valid
+  it "allows single-character usernames" do
+    expect(build(:user, username: "a")).to be_valid
   end
 
-  it "doesn't allow two-character usernames" do
-    expect(build(:user, username: "ab")).not_to be_valid
+  it "allows two-character usernames" do
+    expect(build(:user, username: "ab")).to be_valid
   end
 
   it "allow three-character usernames" do