diff --git a/public/IAdminSystem.h b/public/IAdminSystem.h
index c7fe8454..17317159 100644
--- a/public/IAdminSystem.h
+++ b/public/IAdminSystem.h
@@ -725,7 +725,7 @@ namespace SourceMod
 		 * @param c			Variable to store flag char.
 		 * @return			True on success, false if not found.
 		 */
-		virtual bool FindFlagChar(AdminFlag flag, char *c);
+		virtual bool FindFlagChar(AdminFlag flag, char *c) =0;
 	};
 }