diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 4b6c694a3f7..fc30a52d496 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -4791,7 +4791,9 @@ check_wal_consistency_checking(char **newval, void **extra, GucSource source)
 	list_free(elemlist);
 
 	/* assign new value */
-	*extra = guc_malloc(ERROR, (RM_MAX_ID + 1) * sizeof(bool));
+	*extra = guc_malloc(LOG, (RM_MAX_ID + 1) * sizeof(bool));
+	if (!*extra)
+		return false;
 	memcpy(*extra, newwalconsistency, (RM_MAX_ID + 1) * sizeof(bool));
 	return true;
 }
diff --git a/src/backend/access/transam/xlogrecovery.c b/src/backend/access/transam/xlogrecovery.c
index 2c19013c98b..0aa3ab59085 100644
--- a/src/backend/access/transam/xlogrecovery.c
+++ b/src/backend/access/transam/xlogrecovery.c
@@ -4833,7 +4833,9 @@ check_recovery_target_lsn(char **newval, void **extra, GucSource source)
 		if (have_error)
 			return false;
 
-		myextra = (XLogRecPtr *) guc_malloc(ERROR, sizeof(XLogRecPtr));
+		myextra = (XLogRecPtr *) guc_malloc(LOG, sizeof(XLogRecPtr));
+		if (!myextra)
+			return false;
 		*myextra = lsn;
 		*extra = myextra;
 	}
@@ -4997,7 +4999,9 @@ check_recovery_target_timeline(char **newval, void **extra, GucSource source)
 		}
 	}
 
-	myextra = (RecoveryTargetTimeLineGoal *) guc_malloc(ERROR, sizeof(RecoveryTargetTimeLineGoal));
+	myextra = (RecoveryTargetTimeLineGoal *) guc_malloc(LOG, sizeof(RecoveryTargetTimeLineGoal));
+	if (!myextra)
+		return false;
 	*myextra = rttg;
 	*extra = myextra;
 
@@ -5033,7 +5037,9 @@ check_recovery_target_xid(char **newval, void **extra, GucSource source)
 		if (errno == EINVAL || errno == ERANGE)
 			return false;
 
-		myextra = (TransactionId *) guc_malloc(ERROR, sizeof(TransactionId));
+		myextra = (TransactionId *) guc_malloc(LOG, sizeof(TransactionId));
+		if (!myextra)
+			return false;
 		*myextra = xid;
 		*extra = myextra;
 	}
diff --git a/src/backend/commands/user.c b/src/backend/commands/user.c
index 8ae510c623b..0d638e29d00 100644
--- a/src/backend/commands/user.c
+++ b/src/backend/commands/user.c
@@ -2566,6 +2566,8 @@ check_createrole_self_grant(char **newval, void **extra, GucSource source)
 	list_free(elemlist);
 
 	result = (unsigned *) guc_malloc(LOG, sizeof(unsigned));
+	if (!result)
+		return false;
 	*result = options;
 	*extra = result;
 
diff --git a/src/backend/commands/variable.c b/src/backend/commands/variable.c
index f550a3c0c63..84f044a1959 100644
--- a/src/backend/commands/variable.c
+++ b/src/backend/commands/variable.c
@@ -1087,7 +1087,7 @@ check_application_name(char **newval, void **extra, GucSource source)
 	if (!clean)
 		return false;
 
-	ret = guc_strdup(WARNING, clean);
+	ret = guc_strdup(LOG, clean);
 	if (!ret)
 	{
 		pfree(clean);
@@ -1125,7 +1125,7 @@ check_cluster_name(char **newval, void **extra, GucSource source)
 	if (!clean)
 		return false;
 
-	ret = guc_strdup(WARNING, clean);
+	ret = guc_strdup(LOG, clean);
 	if (!ret)
 	{
 		pfree(clean);
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index 719e531eb90..646ba2a78fa 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -2730,6 +2730,8 @@ check_synchronized_standby_slots(char **newval, void **extra, GucSource source)
 
 	/* GUC extra value must be guc_malloc'd, not palloc'd */
 	config = (SyncStandbySlotsConfigData *) guc_malloc(LOG, size);
+	if (!config)
+		return false;
 
 	/* Transform the data into SyncStandbySlotsConfigData */
 	config->nslotnames = list_length(elemlist);
diff --git a/src/backend/storage/file/fd.c b/src/backend/storage/file/fd.c
index 0c3a2a756e7..84873f41488 100644
--- a/src/backend/storage/file/fd.c
+++ b/src/backend/storage/file/fd.c
@@ -4042,7 +4042,9 @@ check_debug_io_direct(char **newval, void **extra, GucSource source)
 		return result;
 
 	/* Save the flags in *extra, for use by assign_debug_io_direct */
-	*extra = guc_malloc(ERROR, sizeof(int));
+	*extra = guc_malloc(LOG, sizeof(int));
+	if (!*extra)
+		return false;
 	*((int *) *extra) = flags;
 
 	return result;
diff --git a/src/backend/tcop/backend_startup.c b/src/backend/tcop/backend_startup.c
index 27c0b3c2b04..a07c59ece01 100644
--- a/src/backend/tcop/backend_startup.c
+++ b/src/backend/tcop/backend_startup.c
@@ -1078,7 +1078,9 @@ check_log_connections(char **newval, void **extra, GucSource source)
 	 * We succeeded, so allocate `extra` and save the flags there for use by
 	 * assign_log_connections().
 	 */
-	*extra = guc_malloc(ERROR, sizeof(int));
+	*extra = guc_malloc(LOG, sizeof(int));
+	if (!*extra)
+		return false;
 	*((int *) *extra) = flags;
 
 	return true;
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 4d2edb10658..aec65007bb6 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3648,7 +3648,9 @@ check_restrict_nonsystem_relation_kind(char **newval, void **extra, GucSource so
 	list_free(elemlist);
 
 	/* Save the flags in *extra, for use by the assign function */
-	*extra = guc_malloc(ERROR, sizeof(int));
+	*extra = guc_malloc(LOG, sizeof(int));
+	if (!*extra)
+		return false;
 	*((int *) *extra) = flags;
 
 	return true;
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 860bbd40d42..b891dab3bf6 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2198,7 +2198,9 @@ check_backtrace_functions(char **newval, void **extra, GucSource source)
 	 * whitespace chars to save some memory, but it doesn't seem worth the
 	 * trouble.
 	 */
-	someval = guc_malloc(ERROR, newvallen + 1 + 1);
+	someval = guc_malloc(LOG, newvallen + 1 + 1);
+	if (!someval)
+		return false;
 	for (i = 0, j = 0; i < newvallen; i++)
 	{
 		if ((*newval)[i] == ',')
@@ -2283,7 +2285,9 @@ check_log_destination(char **newval, void **extra, GucSource source)
 	pfree(rawstring);
 	list_free(elemlist);
 
-	myextra = (int *) guc_malloc(ERROR, sizeof(int));
+	myextra = (int *) guc_malloc(LOG, sizeof(int));
+	if (!myextra)
+		return false;
 	*myextra = newlogdest;
 	*extra = myextra;
 
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 12192445218..667df448732 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -4909,10 +4909,11 @@ init_custom_variable(const char *name,
 		 strcmp(name, "pljava.vmoptions") == 0))
 		context = PGC_SUSET;
 
-	gen = (struct config_generic *) guc_malloc(ERROR, sz);
+	/* As above, an OOM here is FATAL */
+	gen = (struct config_generic *) guc_malloc(FATAL, sz);
 	memset(gen, 0, sz);
 
-	gen->name = guc_strdup(ERROR, name);
+	gen->name = guc_strdup(FATAL, name);
 	gen->context = context;
 	gen->group = CUSTOM_OPTIONS;
 	gen->short_desc = short_desc;