diff --git a/elixir-mode.el b/elixir-mode.el
index f3674cd3..790611ba 100644
--- a/elixir-mode.el
+++ b/elixir-mode.el
@@ -367,7 +367,9 @@ is used to limit the scan."
      1 font-lock-type-face)
 
     ;; Atoms and singleton-like words like true/false/nil.
-    (,(elixir-rx (group (or atoms "true" "false" "nil"))
+    (,(elixir-rx symbol-start
+                 (group (or atoms "true" "false" "nil"))
+                 symbol-end
                  (zero-or-more space)
                  (optional "="))
      1 elixir-atom-face)
diff --git a/test/elixir-mode-font-test.el b/test/elixir-mode-font-test.el
index 6c82483c..623928e5 100644
--- a/test/elixir-mode-font-test.el
+++ b/test/elixir-mode-font-test.el
@@ -173,6 +173,7 @@ end"
 true
 false
 nil
+true_false_nil
 "
     (should (eq (elixir-test-face-at 3) 'elixir-atom-face))
     (should (eq (elixir-test-face-at 5) 'elixir-atom-face))
@@ -183,7 +184,8 @@ nil
     (should (eq (elixir-test-face-at 26) 'elixir-atom-face))
     (should (eq (elixir-test-face-at 43) 'elixir-atom-face))
     (should (eq (elixir-test-face-at 48) 'elixir-atom-face))
-    (should (eq (elixir-test-face-at 54) 'elixir-atom-face))))
+    (should (eq (elixir-test-face-at 54) 'elixir-atom-face))
+    (should-not (eq (elixir-test-face-at 57) 'elixir-atom-face))))
 
 (ert-deftest elixir-mode-syntax-table/fontify-map-keys ()
   :tags '(fontification map syntax-table)
@@ -246,6 +248,15 @@ some_expr"
    (should (eq (elixir-test-face-at 2) 'font-lock-variable-name-face))
    (should (eq (elixir-test-face-at 4) 'font-lock-variable-name-face))))
 
+(ert-deftest elixir-mode-syntax-table/fontify-assignment-with-singleton ()
+  "https://github.com/elixir-lang/emacs-elixir/issues/245"
+  :tags '(fontification syntax-table)
+  (elixir-test-with-temp-buffer
+   "true_false_nil = 1"
+   (should (eq (elixir-test-face-at 1) 'font-lock-variable-name-face))
+   (should (eq (elixir-test-face-at 6) 'font-lock-variable-name-face))
+   (should (eq (elixir-test-face-at 12) 'font-lock-variable-name-face))))
+
 (provide 'elixir-mode-font-test)
 
 ;;; elixir-mode-font-test.el ends here