diff --git a/src/config_parser.cpp b/src/config_parser.cpp
index 1e8e646..74a47ba 100644
--- a/src/config_parser.cpp
+++ b/src/config_parser.cpp
@@ -123,12 +123,12 @@
     setFile(filename);
 }
 
-inline bool isspace(char c) noexcept
+constexpr bool isspace(char c) noexcept
 {
     return c == ' ' || c == '\t';
 }
 
-inline bool iscomment(char c) noexcept
+constexpr bool iscomment(char c) noexcept
 {
     return c == '#' || c == ';';
 }