diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index a3e8ce092f..b8f648927a 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -4799,6 +4799,22 @@ check_wal_buffers(int *newval, void **extra, GucSource source)
 	return true;
 }
 
+/*
+ * Read the control file, set respective GUCs.
+ *
+ * This is to be called during startup, unless in bootstrap mode, where no
+ * control file yet exists.  As there's no shared memory yet (its sizing can
+ * depend on the contents of the control file!), first store data in local
+ * memory. XLOGShemInit() will then copy it to shared memory later.
+ */
+void
+LocalProcessControlFile(void)
+{
+	Assert(ControlFile == NULL);
+	ControlFile = palloc(sizeof(ControlFileData));
+	ReadControlFile();
+}
+
 /*
  * Initialization of shared memory for XLOG
  */
@@ -4850,6 +4866,7 @@ XLOGShmemInit(void)
 				foundXLog;
 	char	   *allocptr;
 	int			i;
+	ControlFileData *localControlFile;
 
 #ifdef WAL_DEBUG
 
@@ -4867,8 +4884,18 @@ XLOGShmemInit(void)
 	}
 #endif
 
+	/*
+	 * Already have read control file locally, unless in bootstrap mode. Move
+	 * local version into shared memory.
+	 */
+	localControlFile = ControlFile;
 	ControlFile = (ControlFileData *)
 		ShmemInitStruct("Control File", sizeof(ControlFileData), &foundCFile);
+	if (localControlFile)
+	{
+		memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+		pfree(localControlFile);
+	}
 	XLogCtl = (XLogCtlData *)
 		ShmemInitStruct("XLOG Ctl", XLOGShmemSize(), &foundXLog);
 
@@ -4933,14 +4960,6 @@ XLOGShmemInit(void)
 	SpinLockInit(&XLogCtl->info_lck);
 	SpinLockInit(&XLogCtl->ulsn_lck);
 	InitSharedLatch(&XLogCtl->recoveryWakeupLatch);
-
-	/*
-	 * If we are not in bootstrap mode, pg_control should already exist. Read
-	 * and validate it immediately (see comments in ReadControlFile() for the
-	 * reasons why).
-	 */
-	if (!IsBootstrapProcessingMode())
-		ReadControlFile();
 }
 
 /*
@@ -5129,6 +5148,12 @@ BootStrapXLOG(void)
 	BootStrapMultiXact();
 
 	pfree(buffer);
+
+	/*
+	 * Force control file to be read - in contrast to normal processing we'd
+	 * otherwise never run the checks and GUC related initializations therein.
+	 */
+	ReadControlFile();
 }
 
 static char *
@@ -6227,13 +6252,8 @@ StartupXLOG(void)
 	struct stat st;
 
 	/*
-	 * Read control file and check XLOG status looks valid.
-	 *
-	 * Note: in most control paths, *ControlFile is already valid and we need
-	 * not do ReadControlFile() here, but might as well do it to be sure.
+	 * Verify XLOG status looks valid.
 	 */
-	ReadControlFile();
-
 	if (ControlFile->state < DB_SHUTDOWNED ||
 		ControlFile->state > DB_IN_PRODUCTION ||
 		!XRecOffIsValid(ControlFile->checkPoint))
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 95180b2ef5..e4f8f597c6 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -950,6 +950,9 @@ PostmasterMain(int argc, char *argv[])
 	 */
 	CreateDataDirLockFile(true);
 
+	/* read control file (error checking and contains config) */
+	LocalProcessControlFile();
+
 	/*
 	 * Initialize SSL library, if specified.
 	 */
@@ -4805,6 +4808,9 @@ SubPostmasterMain(int argc, char *argv[])
 	/* Read in remaining GUC variables */
 	read_nondefault_variables();
 
+	/* (re-)read control file (contains config) */
+	LocalProcessControlFile();
+
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 4eb85720a7..46b662266b 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3717,6 +3717,9 @@ PostgresMain(int argc, char *argv[],
 		 */
 		CreateDataDirLockFile(false);
 
+		/* read control file (error checking and contains config ) */
+		LocalProcessControlFile();
+
 		/* Initialize MaxBackends (if under postmaster, was done already) */
 		InitializeMaxBackends();
 	}
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 66bfb77295..e0635ab4e6 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -261,6 +261,7 @@ extern XLogRecPtr GetFakeLSNForUnloggedRel(void);
 extern Size XLOGShmemSize(void);
 extern void XLOGShmemInit(void);
 extern void BootStrapXLOG(void);
+extern void LocalProcessControlFile(void);
 extern void StartupXLOG(void);
 extern void ShutdownXLOG(int code, Datum arg);
 extern void InitXLOGAccess(void);