diff --git a/.travis.yml b/.travis.yml
index e200666..d2e5340 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -39,6 +39,34 @@ matrix:
       env:
         - CXX_COMPILER=g++-9 CC_COMPILER=gcc-9
 
+    - os: linux
+      compiler: clang++
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+            - sourceline: 'deb https://apt.llvm.org/xenial/ llvm-toolchain-xenial-5 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
+          packages:
+            - g++-7
+            - clang-5
+      env:
+        - CXX_COMPILER=clang++-5 CC_COMPILER=clang-5
+
+    - os: linux
+      compiler: clang++
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+            - sourceline: 'deb https://apt.llvm.org/xenial/ llvm-toolchain-xenial-6 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
+          packages:
+            - g++-7
+            - clang-6
+      env:
+        - CXX_COMPILER=clang++-6 CC_COMPILER=clang-6
+
     - os: linux
       compiler: clang++
       addons:
diff --git a/README.md b/README.md
index 83c70ad..c25bd84 100644
--- a/README.md
+++ b/README.md
@@ -113,7 +113,7 @@ If you are using [Conan](https://www.conan.io/) to manage your dependencies, mer
 
 ## Compiler compatibility
 
-* Clang/LLVM >= 7
+* Clang/LLVM >= 5
 * Visual C++ >= 15.3 / Visual Studio >= 2017
 * Xcode >= 10
 * GCC >= 7 (GCC >= 9 for NAMEOF_ENUM)
diff --git a/include/nameof.hpp b/include/nameof.hpp
index e6fbc74..abdad34 100644
--- a/include/nameof.hpp
+++ b/include/nameof.hpp
@@ -94,6 +94,15 @@ class [[nodiscard]] cstring {
 
   std::array<char, N + 1> chars_;
 
+  constexpr auto to_chars(std::string_view str) noexcept {
+    assert(str.size() == N);
+    decltype(chars_) chars = {};
+    for (std::size_t i = 0; i < str.size() && i < N; ++i) {
+      chars[i] = str[i];
+    }
+    return chars;
+  }
+
  public:
   using value_type      = char;
   using size_type       = std::size_t;
@@ -109,12 +118,7 @@ class [[nodiscard]] cstring {
   using reverse_iterator       = std::reverse_iterator<iterator>;
   using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
-  constexpr explicit cstring(std::string_view str) noexcept : chars_{} {
-    assert(str.size() == N);
-    for (std::size_t i = 0; i < N; ++i) {
-      chars_[i] = str[i];
-    }
-  }
+  constexpr explicit cstring(std::string_view str) noexcept : chars_{to_chars(str)} {}
 
   constexpr cstring() = delete;