diff --git a/src/support/lockedpool.cpp b/src/support/lockedpool.cpp
index 01eef2b93d3..c27f900d021 100644
--- a/src/support/lockedpool.cpp
+++ b/src/support/lockedpool.cpp
@@ -400,3 +400,10 @@ void LockedPoolManager::CreateInstance()
     static LockedPoolManager instance(std::move(allocator));
     LockedPoolManager::_instance = &instance;
 }
+
+LockedPoolManager& LockedPoolManager::Instance()
+{
+    static std::once_flag init_flag;
+    std::call_once(init_flag, LockedPoolManager::CreateInstance);
+    return *LockedPoolManager::_instance;
+}
diff --git a/src/support/lockedpool.h b/src/support/lockedpool.h
index 2363b1e4ef0..a7d80df8766 100644
--- a/src/support/lockedpool.h
+++ b/src/support/lockedpool.h
@@ -219,12 +219,7 @@ class LockedPoolManager : public LockedPool
 {
 public:
     /** Return the current instance, or create it once */
-    static LockedPoolManager& Instance()
-    {
-        static std::once_flag init_flag;
-        std::call_once(init_flag, LockedPoolManager::CreateInstance);
-        return *LockedPoolManager::_instance;
-    }
+    static LockedPoolManager& Instance();
 
 private:
     explicit LockedPoolManager(std::unique_ptr<LockedPageAllocator> allocator);