diff --git a/source/blender/animrig/ANIM_action_legacy.hh b/source/blender/animrig/ANIM_action_legacy.hh
index 7df85730eb7..0db60037ab2 100644
--- a/source/blender/animrig/ANIM_action_legacy.hh
+++ b/source/blender/animrig/ANIM_action_legacy.hh
@@ -49,6 +49,14 @@ ChannelBag &channelbag_ensure(Action &action);
 Vector<const FCurve *> fcurves_all(const bAction *action);
 Vector<FCurve *> fcurves_all(bAction *action);
 
+/**
+ * Return the F-Curves for the first slot of this Action.
+ *
+ * This works for both legacy and layered Actions. For the former, it will
+ * return all F-Curves in the Action.
+ */
+Vector<FCurve *> fcurves_first_slot(bAction *action);
+
 /**
  * Return the F-Curves for this specific slot handle.
  *
diff --git a/source/blender/animrig/intern/action_legacy.cc b/source/blender/animrig/intern/action_legacy.cc
index f8cb8a0a845..a2b075cd965 100644
--- a/source/blender/animrig/intern/action_legacy.cc
+++ b/source/blender/animrig/intern/action_legacy.cc
@@ -124,6 +124,23 @@ Vector<const FCurve *> fcurves_all(const bAction *action)
                                const ChannelBag>(action->wrap());
 }
 
+Vector<FCurve *> fcurves_first_slot(bAction *action)
+{
+  if (!action) {
+    return {};
+  }
+  Action &action_wrap = action->wrap();
+
+  if (action_wrap.is_action_legacy()) {
+    return fcurves_all(action);
+  }
+
+  if (action_wrap.slots().is_empty()) {
+    return {};
+  }
+  return fcurves_for_action_slot(action, action_wrap.slot(0)->handle);
+}
+
 /* Lots of template args to support transparent non-const and const versions. */
 template<typename ActionType,
          typename FCurveType,
diff --git a/source/blender/blenkernel/BKE_fcurve.hh b/source/blender/blenkernel/BKE_fcurve.hh
index 8e606c27798..6885e088cef 100644
--- a/source/blender/blenkernel/BKE_fcurve.hh
+++ b/source/blender/blenkernel/BKE_fcurve.hh
@@ -9,7 +9,9 @@
  */
 
 #include "BLI_math_vector_types.hh"
+#include "BLI_span.hh"
 #include "BLI_string_ref.hh"
+
 #include "DNA_curve_types.h"
 
 struct ChannelDriver;
@@ -348,7 +350,7 @@ int BKE_fcurve_bezt_binarysearch_index(const BezTriple array[],
 /**
  * Cached f-curve look-ups, use when this needs to be done many times.
  */
-FCurvePathCache *BKE_fcurve_pathcache_create(ListBase *list);
+FCurvePathCache *BKE_fcurve_pathcache_create(blender::Span<FCurve *> fcurves);
 void BKE_fcurve_pathcache_destroy(FCurvePathCache *fcache);
 FCurve *BKE_fcurve_pathcache_find(FCurvePathCache *fcache, const char rna_path[], int array_index);
 /**
diff --git a/source/blender/blenkernel/intern/action_mirror.cc b/source/blender/blenkernel/intern/action_mirror.cc
index 5e3c39bda4a..a035cd7f96e 100644
--- a/source/blender/blenkernel/intern/action_mirror.cc
+++ b/source/blender/blenkernel/intern/action_mirror.cc
@@ -31,6 +31,8 @@
 
 #include "DEG_depsgraph.hh"
 
+using namespace blender;
+
 /* -------------------------------------------------------------------- */
 /** \name Flip the Action (Armature/Pose Objects)
  *
@@ -451,7 +453,8 @@ static void action_flip_pchan_rna_paths(bAction *act)
 
 void BKE_action_flip_with_pose(bAction *act, Object *ob_arm)
 {
-  FCurvePathCache *fcache = BKE_fcurve_pathcache_create(&act->curves);
+  Vector<FCurve *> fcurves = animrig::legacy::fcurves_first_slot(act);
+  FCurvePathCache *fcache = BKE_fcurve_pathcache_create(fcurves);
   int i;
   LISTBASE_FOREACH_INDEX (bPoseChannel *, pchan, &ob_arm->pose->chanbase, i) {
     action_flip_pchan(ob_arm, pchan, fcache);
diff --git a/source/blender/blenkernel/intern/fcurve_cache.cc b/source/blender/blenkernel/intern/fcurve_cache.cc
index fbbafb035ff..ed424d0d4ef 100644
--- a/source/blender/blenkernel/intern/fcurve_cache.cc
+++ b/source/blender/blenkernel/intern/fcurve_cache.cc
@@ -63,14 +63,13 @@ static int fcurve_cmp_for_cache(const void *fcu_a_p, const void *fcu_b_p)
   return 0;
 }
 
-FCurvePathCache *BKE_fcurve_pathcache_create(ListBase *list)
+FCurvePathCache *BKE_fcurve_pathcache_create(blender::Span<FCurve *> fcurves)
 {
-  const uint fcurve_array_len = BLI_listbase_count(list);
+  const uint fcurve_array_len = fcurves.size();
   FCurve **fcurve_array = static_cast<FCurve **>(
       MEM_mallocN(sizeof(*fcurve_array) * fcurve_array_len, __func__));
-  uint i;
-  LISTBASE_FOREACH_INDEX (FCurve *, fcu, list, i) {
-    fcurve_array[i] = fcu;
+  for (const int i : fcurves.index_range()) {
+    fcurve_array[i] = fcurves[i];
   }
   qsort(fcurve_array, fcurve_array_len, sizeof(FCurve *), fcurve_cmp_for_cache);
 
@@ -83,7 +82,7 @@ FCurvePathCache *BKE_fcurve_pathcache_create(ListBase *list)
   /* May over reserve, harmless. */
   GHash *span_from_rna_path = BLI_ghash_str_new_ex(__func__, fcurve_array_len);
   uint span_index = 0;
-  i = 0;
+  uint i = 0;
   while (i < fcurve_array_len) {
     uint i_end;
     for (i_end = i + 1; i_end < fcurve_array_len; i_end++) {