diff --git a/hal/src/main/native/include/MockData/NotifyListenerVector.h b/hal/src/main/native/include/MockData/NotifyListenerVector.h
index 716478418b..d437535f8f 100644
--- a/hal/src/main/native/include/MockData/NotifyListenerVector.h
+++ b/hal/src/main/native/include/MockData/NotifyListenerVector.h
@@ -10,8 +10,8 @@
 #ifndef __FRC_ROBORIO__
 
 #include <memory>
-#include <queue>
-#include <vector>
+
+#include <wpi/SmallVector.h>
 
 #include "NotifyListener.h"
 
@@ -24,8 +24,8 @@ class HalCallbackListenerVectorImpl {
   struct private_init {};
 
  public:
-  typedef typename std::vector<HalCallbackListener<ListenerType>>::size_type
-      size_type;
+  typedef typename wpi::SmallVectorImpl<
+      HalCallbackListener<ListenerType>>::size_type size_type;
 
   // Constructor for creating copies of the vector
   HalCallbackListenerVectorImpl(const HalCallbackListenerVectorImpl* copyFrom,
@@ -64,8 +64,8 @@ class HalCallbackListenerVectorImpl {
       unsigned int uid);
 
  private:
-  std::vector<HalCallbackListener<ListenerType>> m_vector;
-  std::vector<unsigned int> m_free;
+  wpi::SmallVector<HalCallbackListener<ListenerType>, 4> m_vector;
+  wpi::SmallVector<unsigned int, 4> m_free;
 
   // Add a new NotifyListener to the vector.  If there are elements on the
   // freelist,