diff --git a/tests/test_checker.py b/tests/test_checker.py
index af6dfd0..b7f9f6a 100644
--- a/tests/test_checker.py
+++ b/tests/test_checker.py
@@ -37,3 +37,5 @@ def test_checker_floats(self):
     self.assertFalse(checker_floats(correct, output))
     output = "1 or 0.4e-1"
     self.assertTrue(checker_floats(correct, output, eps = 0.01))
+    # Check NaN
+    self.assertFalse(checker_floats("1", "nan"))
diff --git a/tools/checkers.py b/tools/checkers.py
index f2fc776..fe6b776 100644
--- a/tools/checkers.py
+++ b/tools/checkers.py
@@ -1,3 +1,5 @@
+from math import isnan
+
 """Author: Andrey Malevich
 This module contains different checkers which are used to test outputs of
 programs.
@@ -71,6 +73,8 @@ def checker_floats(correct, output, eps = 1e-6):
     try: #Otherwise we assume that they are floats
       first = float(first)
       second = float(second)
+      if isnan(first) or isnan(second):
+        return False
       if first > second + eps or second > first + eps:  #In case they differ in
           # more than eps
         return False