diff --git a/include/jwt/base64.hpp b/include/jwt/base64.hpp
index 577d468..2f2a646 100644
--- a/include/jwt/base64.hpp
+++ b/include/jwt/base64.hpp
@@ -64,12 +64,12 @@ public:
   }
 
 private:
-  std::array<char, 64> chars_ = {
+  std::array<char, 64> chars_ = {{
     'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z',
     'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z',
     '0','1','2','3','4','5','6','7','8','9',
     '+','/',
-  };
+  }};
 };
 
 /**
@@ -158,7 +158,7 @@ public:
   }
 
 private:
-  std::array<char, 256> map_ = {
+  std::array<char, 256> map_ = {{
     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, //   0-15
     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, //  16-31
     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, //  32-47
@@ -175,7 +175,7 @@ private:
     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 208-223
     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 224-239
     -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1  // 240-255
-  };
+  }};
 };
 
 /**