diff --git a/include/etl/char_traits.h b/include/etl/char_traits.h
index 23fd4b06..25ed1638 100644
--- a/include/etl/char_traits.h
+++ b/include/etl/char_traits.h
@@ -139,17 +139,19 @@ namespace etl
     //*************************************************************************
     static ETL_CONSTEXPR14 size_t length(const char_type* begin)
     {
-      const char_type* end = begin;
-
-      if (end != 0)
+      if (begin == ETL_NULLPTR)
       {
-        while (*end++ != 0)
-        {
-          // Do nothing.
-        }
+        return 0;
       }
 
-      return size_t(end - begin);
+      const char_type* end = begin;
+
+      while (*end++ != 0)
+      {
+        // Do nothing.
+      }
+
+      return size_t(end - begin) - 1;
     }
 
     //*************************************************************************
diff --git a/test/test_char_traits.cpp b/test/test_char_traits.cpp
index ecdf136e..75b6dad3 100644
--- a/test/test_char_traits.cpp
+++ b/test/test_char_traits.cpp
@@ -55,6 +55,16 @@ namespace
     //*************************************************************************
     TEST(test_strlen)
     {
+      CHECK_EQUAL(0U, etl::strlen((const char*)0));
+      CHECK_EQUAL(0U, etl::strlen((const wchar_t*)0));
+      CHECK_EQUAL(0U, etl::strlen((const char16_t*)0));
+      CHECK_EQUAL(0U, etl::strlen((const char32_t*)0));
+
+      CHECK_EQUAL(0U, etl::strlen(""));
+      CHECK_EQUAL(0U, etl::strlen(L""));
+      CHECK_EQUAL(0U, etl::strlen(u""));
+      CHECK_EQUAL(0U, etl::strlen(U""));
+
       CHECK_EQUAL(6U, etl::strlen("qwerty"));
       CHECK_EQUAL(6U, etl::strlen(L"qwerty"));
       CHECK_EQUAL(6U, etl::strlen(u"qwerty"));