diff --git a/src/ConfigData.cxx b/src/ConfigData.cxx
index b3c5c75fc..cd4e34a94 100644
--- a/src/ConfigData.cxx
+++ b/src/ConfigData.cxx
@@ -63,7 +63,7 @@ block_param::GetBoolValue() const
 }
 
 config_param::config_param(const char *_value, int _line)
-	:next(nullptr), value(_value), line(_line) {}
+	:next(nullptr), value(_value), line(_line), used(false) {}
 
 config_param::~config_param()
 {