diff --git a/include/pcmki/pcmki_scheduler.h b/include/pcmki/pcmki_scheduler.h
index c604a32458..f2f3d5bf61 100644
--- a/include/pcmki/pcmki_scheduler.h
+++ b/include/pcmki/pcmki_scheduler.h
@@ -1,110 +1,136 @@
 /*
  * Copyright 2014-2021 the Pacemaker project contributors
  *
  * The version control history for this file may have further details.
  *
  * This source code is licensed under the GNU Lesser General Public License
  * version 2.1 or later (LGPLv2.1+) WITHOUT ANY WARRANTY.
  */
 
 #ifndef PENGINE__H
 #  define PENGINE__H
 
 typedef struct rsc_ticket_s rsc_ticket_t;
 typedef struct lrm_agent_s lrm_agent_t;
 
 #  include <glib.h>
 #  include <crm/crm.h>
 #  include <crm/common/iso8601.h>
 #  include <crm/pengine/rules.h>
 #  include <crm/pengine/common.h>
 #  include <crm/pengine/status.h>
 
 #  include <crm/pengine/complex.h>
 
 enum pe_stop_fail {
     pesf_block,
     pesf_stonith,
     pesf_ignore
 };
 
 enum pe_weights {
     pe_weights_none = 0x0,
     pe_weights_init = 0x1,
     pe_weights_forward = 0x4,
     pe_weights_positive = 0x8,
     pe_weights_rollback = 0x10,
 };
 
 typedef struct {
     const char *id;
     const char *node_attribute;
     pe_resource_t *rsc_lh;
     pe_resource_t *rsc_rh;
 
     int role_lh;
     int role_rh;
 
     int score;
     bool influence; // Whether rsc_lh should influence active rsc_rh placement
 } pcmk__colocation_t;
 
 enum loss_ticket_policy_e {
     loss_ticket_stop,
     loss_ticket_demote,
     loss_ticket_fence,
     loss_ticket_freeze
 };
 
 struct rsc_ticket_s {
     const char *id;
     pe_resource_t *rsc_lh;
     pe_ticket_t *ticket;
     enum loss_ticket_policy_e loss_policy;
 
     int role_lh;
 };
 
 extern gboolean stage0(pe_working_set_t * data_set);
 extern gboolean probe_resources(pe_working_set_t * data_set);
 extern gboolean stage2(pe_working_set_t * data_set);
 extern gboolean stage3(pe_working_set_t * data_set);
 extern gboolean stage4(pe_working_set_t * data_set);
 extern gboolean stage5(pe_working_set_t * data_set);
 extern gboolean stage6(pe_working_set_t * data_set);
 extern gboolean stage7(pe_working_set_t * data_set);
 extern gboolean stage8(pe_working_set_t * data_set);
 
 extern gboolean summary(GListPtr resources);
 
 extern gboolean unpack_constraints(xmlNode * xml_constraints, pe_working_set_t * data_set);
 
 extern gboolean shutdown_constraints(pe_node_t * node, pe_action_t * shutdown_op,
                                      pe_working_set_t * data_set);
 
 void pcmk__order_vs_fence(pe_action_t *stonith_op, pe_working_set_t *data_set);
 
 extern int custom_action_order(pe_resource_t * lh_rsc, char *lh_task, pe_action_t * lh_action,
                                pe_resource_t * rh_rsc, char *rh_task, pe_action_t * rh_action,
                                enum pe_ordering type, pe_working_set_t * data_set);
 
 extern int new_rsc_order(pe_resource_t * lh_rsc, const char *lh_task,
                          pe_resource_t * rh_rsc, const char *rh_task,
                          enum pe_ordering type, pe_working_set_t * data_set);
 
 #  define order_start_start(rsc1,rsc2, type)				\
     new_rsc_order(rsc1, CRMD_ACTION_START, rsc2, CRMD_ACTION_START, type, data_set)
 #  define order_stop_stop(rsc1, rsc2, type)				\
     new_rsc_order(rsc1, CRMD_ACTION_STOP, rsc2, CRMD_ACTION_STOP, type, data_set)
 
 extern void graph_element_from_action(pe_action_t * action, pe_working_set_t * data_set);
 extern void add_maintenance_update(pe_working_set_t *data_set);
 xmlNode *pcmk__schedule_actions(pe_working_set_t *data_set, xmlNode *xml_input,
                                 crm_time_t *now);
 bool pcmk__ordering_is_invalid(pe_action_t *action, pe_action_wrapper_t *input);
 
 extern gboolean show_scores;
 extern gboolean show_utilization;
 extern const char *transition_idle_timeout;
 
+/*!
+ * \internal
+ * \brief Check whether colocation's left-hand preferences should be considered
+ *
+ * \param[in] colocation  Colocation constraint
+ * \param[in] rsc         Right-hand instance (normally this will be
+ *                        colocation->rsc_rh, which NULL will be treated as,
+ *                        but for clones or bundles with multiple instances
+ *                        this can be a particular instance)
+ *
+ * \return true if colocation influence should be effective, otherwise false
+ */
+static inline bool
+pcmk__colocation_has_influence(const pcmk__colocation_t *colocation,
+                               const pe_resource_t *rsc)
+{
+    if (rsc == NULL) {
+        rsc = colocation->rsc_rh;
+    }
+
+    /* The left hand of a colocation influences the right hand's location
+     * if the influence option is true, or the right hand is not yet active.
+     */
+    return colocation->influence || (rsc->running_on == NULL);
+}
+
 #endif