diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 429c055489..a4574cd533 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -158,7 +158,7 @@ extern PGDLLIMPORT int NBuffers;
 extern PGDLLIMPORT int MaxBackends;
 extern PGDLLIMPORT int MaxConnections;
 extern PGDLLIMPORT int max_worker_processes;
-extern int	max_parallel_workers;
+extern PGDLLIMPORT int max_parallel_workers;
 
 extern PGDLLIMPORT int MyProcPid;
 extern PGDLLIMPORT pg_time_t MyStartTime;
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index d2fff76653..0e9f858b9e 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -53,24 +53,24 @@ extern PGDLLIMPORT double cpu_operator_cost;
 extern PGDLLIMPORT double parallel_tuple_cost;
 extern PGDLLIMPORT double parallel_setup_cost;
 extern PGDLLIMPORT int effective_cache_size;
-extern Cost disable_cost;
-extern int	max_parallel_workers_per_gather;
-extern bool enable_seqscan;
-extern bool enable_indexscan;
-extern bool enable_indexonlyscan;
-extern bool enable_bitmapscan;
-extern bool enable_tidscan;
-extern bool enable_sort;
-extern bool enable_hashagg;
-extern bool enable_nestloop;
-extern bool enable_material;
-extern bool enable_mergejoin;
-extern bool enable_hashjoin;
-extern bool enable_gathermerge;
-extern bool enable_partition_wise_join;
-extern bool enable_parallel_append;
-extern bool enable_parallel_hash;
-extern int	constraint_exclusion;
+extern PGDLLIMPORT Cost disable_cost;
+extern PGDLLIMPORT int	max_parallel_workers_per_gather;
+extern PGDLLIMPORT bool enable_seqscan;
+extern PGDLLIMPORT bool enable_indexscan;
+extern PGDLLIMPORT bool enable_indexonlyscan;
+extern PGDLLIMPORT bool enable_bitmapscan;
+extern PGDLLIMPORT bool enable_tidscan;
+extern PGDLLIMPORT bool enable_sort;
+extern PGDLLIMPORT bool enable_hashagg;
+extern PGDLLIMPORT bool enable_nestloop;
+extern PGDLLIMPORT bool enable_material;
+extern PGDLLIMPORT bool enable_mergejoin;
+extern PGDLLIMPORT bool enable_hashjoin;
+extern PGDLLIMPORT bool enable_gathermerge;
+extern PGDLLIMPORT bool enable_partition_wise_join;
+extern PGDLLIMPORT bool enable_parallel_append;
+extern PGDLLIMPORT bool enable_parallel_hash;
+extern PGDLLIMPORT int	constraint_exclusion;
 
 extern double clamp_row_est(double nrows);
 extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
diff --git a/src/include/optimizer/paths.h b/src/include/optimizer/paths.h
index b6be259ff7..4708443c39 100644
--- a/src/include/optimizer/paths.h
+++ b/src/include/optimizer/paths.h
@@ -20,10 +20,10 @@
 /*
  * allpaths.c
  */
-extern bool enable_geqo;
-extern int	geqo_threshold;
-extern int	min_parallel_table_scan_size;
-extern int	min_parallel_index_scan_size;
+extern PGDLLIMPORT bool enable_geqo;
+extern PGDLLIMPORT int	geqo_threshold;
+extern PGDLLIMPORT int	min_parallel_table_scan_size;
+extern PGDLLIMPORT int	min_parallel_index_scan_size;
 
 /* Hook for plugins to get control in set_rel_pathlist() */
 typedef void (*set_rel_pathlist_hook_type) (PlannerInfo *root,
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 77daa5a539..2e03640c0b 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -263,7 +263,7 @@ extern char *HbaFileName;
 extern char *IdentFileName;
 extern char *external_pid_file;
 
-extern char *application_name;
+extern PGDLLIMPORT char *application_name;
 
 extern int	tcp_keepalives_idle;
 extern int	tcp_keepalives_interval;