diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 3719bbc7c..3a57356ab 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -54,6 +54,7 @@ else()
     add_compile_options(
         -Wall
         -Werror=implicit-fallthrough
+        -Werror=missing-declarations
         -Werror=reorder
         -Wextra
         -Wmissing-declarations