diff --git a/libprocessgroup/processgroup.cpp b/libprocessgroup/processgroup.cpp
index 9af2682..d352f0e 100644
--- a/libprocessgroup/processgroup.cpp
+++ b/libprocessgroup/processgroup.cpp
@@ -275,7 +275,7 @@
     return empty;
 }
 
-void removeAllProcessGroupsInternal(bool empty_only) {
+static void removeAllProcessGroupsInternal(bool empty_only) {
     std::vector<std::string> cgroups;
     std::string path, memcg_apps_path;