diff --git a/CMakeLists.txt b/CMakeLists.txt
index b3ebd20..8d3d826 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,7 +2,7 @@
 cmake_minimum_required(VERSION 3.10)
 project(cpp-dotenv VERSION 0.2.0)
 
-set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 #----------------------- LIBRARY CONFIGURATION -------------------------
diff --git a/dotenv.h b/dotenv.h
index 7133af2..a5fad3c 100644
--- a/dotenv.h
+++ b/dotenv.h
@@ -444,7 +444,7 @@ namespace dotenv
     };
 
 
-    const container parser::SP
+    inline const container parser::SP
     {
         container::CHAR_MODE::INCLUDE,
         SP_C,
@@ -452,7 +452,7 @@ namespace dotenv
     };
 
 
-    const container parser::UNQUOTED_KEY_CHAR
+    inline const container parser::UNQUOTED_KEY_CHAR
     {
         container::CHAR_MODE::EXCLUDE,
         CS_C,
@@ -466,7 +466,7 @@ namespace dotenv
     };
 
 
-    const container parser::UNQUOTED_VALUE_CHAR
+    inline const container parser::UNQUOTED_VALUE_CHAR
     {
         container::CHAR_MODE::EXCLUDE,
         CS_C,
@@ -479,14 +479,14 @@ namespace dotenv
     };
 
 
-    const container parser::UNQUOTED_COMMENT_CHAR
+    inline const container parser::UNQUOTED_COMMENT_CHAR
     {
         container::CHAR_MODE::EXCLUDE,
         NL_C,
         CR_C
     };
 
-    const std::vector<std::pair<char, char>> parser::ESCAPED_EQUIVALENCES
+    inline const std::vector<std::pair<char, char>> parser::ESCAPED_EQUIVALENCES
     {
         { '?' , '?'  },
         { '\'', '\'' },
@@ -570,9 +570,9 @@ namespace dotenv
     };
 
 
-    const std::string dotenv::env_filename = ".env";
-    dotenv dotenv::_instance;
+    inline const std::string dotenv::env_filename = ".env";
+    inline dotenv dotenv::_instance;
 
 
-    dotenv& env = dotenv::instance().load_dotenv();
+    inline dotenv& env = dotenv::instance().load_dotenv();
 }