diff --git a/src/unity.c b/src/unity.c
index 0219b37268ccf089241ec94cccaee88b6865f1d0..3787591ef2d0ca685f95cfff0c3f11db4f4075bd 100644
--- a/src/unity.c
+++ b/src/unity.c
@@ -578,7 +578,8 @@ void UnityAssertFloatsWithin(const _UF delta,
         pos_delta = 0.0f - pos_delta;
     }
 
-    if (pos_delta < diff)
+    // NOTE: This comparrison is deliberately this way round so that NaNs fail.
+    if ( ! (pos_delta >= diff) )
     {
         UnityTestResultsFailBegin(lineNumber);
 #ifdef UNITY_FLOAT_VERBOSE
diff --git a/test/testunity.c b/test/testunity.c
index e98ca8f9df93e83d4ccc67ad368bcbfae1a1db33..ddd80c52ab7bc79f41a91ab32694642cde44c8c8 100755
--- a/test/testunity.c
+++ b/test/testunity.c
@@ -2226,6 +2226,17 @@ void testFloatsNotEqualNegative2(void)
 #endif
 }
 
+void testFloatsNotEqualActualNaN(void)
+{
+#ifdef UNITY_EXCLUDE_FLOAT
+    TEST_IGNORE();
+#else
+    EXPECT_ABORT_BEGIN
+    TEST_ASSERT_EQUAL_FLOAT(85.963f, 0.0f / 0.0f);
+    VERIFY_FAILS_END
+#endif
+}
+
 void testEqualFloatArrays(void)
 {
 #ifdef UNITY_EXCLUDE_FLOAT