diff --git a/src/backend/access/rmgrdesc/heapdesc.c b/src/backend/access/rmgrdesc/heapdesc.c
index d73248abdd..f382c0f623 100644
--- a/src/backend/access/rmgrdesc/heapdesc.c
+++ b/src/backend/access/rmgrdesc/heapdesc.c
@@ -47,7 +47,7 @@ infobits_desc(StringInfo buf, uint8 infobits, const char *keyname)
 		buf->data[buf->len] = '\0';
 	}
 
-	appendStringInfoString(buf, "]");
+	appendStringInfoChar(buf, ']');
 }
 
 static void
@@ -68,7 +68,7 @@ truncate_flags_desc(StringInfo buf, uint8 flags)
 		buf->data[buf->len] = '\0';
 	}
 
-	appendStringInfoString(buf, "]");
+	appendStringInfoChar(buf, ']');
 }
 
 static void
@@ -88,7 +88,7 @@ plan_elem_desc(StringInfo buf, void *plan, void *data)
 
 	*offsets += new_plan->ntuples;
 
-	appendStringInfo(buf, " }");
+	appendStringInfoString(buf, " }");
 }
 
 void
diff --git a/src/backend/access/rmgrdesc/nbtdesc.c b/src/backend/access/rmgrdesc/nbtdesc.c
index e4fbaa4d5d..f3d725a274 100644
--- a/src/backend/access/rmgrdesc/nbtdesc.c
+++ b/src/backend/access/rmgrdesc/nbtdesc.c
@@ -248,5 +248,5 @@ delvacuum_desc(StringInfo buf, char *block_data,
 			((char *) updates + SizeOfBtreeUpdate +
 			 updates->ndeletedtids * sizeof(uint16));
 	}
-	appendStringInfoString(buf, "]");
+	appendStringInfoChar(buf, ']');
 }
diff --git a/src/backend/access/rmgrdesc/rmgrdesc_utils.c b/src/backend/access/rmgrdesc/rmgrdesc_utils.c
index 808770524d..ef89179bb4 100644
--- a/src/backend/access/rmgrdesc/rmgrdesc_utils.c
+++ b/src/backend/access/rmgrdesc/rmgrdesc_utils.c
@@ -37,7 +37,7 @@ array_desc(StringInfo buf, void *array, size_t elem_size, int count,
 		if (i < count - 1)
 			appendStringInfoString(buf, ", ");
 	}
-	appendStringInfoString(buf, "]");
+	appendStringInfoChar(buf, ']');
 }
 
 void
diff --git a/src/backend/access/transam/xlogbackup.c b/src/backend/access/transam/xlogbackup.c
index 23461c9d2c..21d68133ae 100644
--- a/src/backend/access/transam/xlogbackup.c
+++ b/src/backend/access/transam/xlogbackup.c
@@ -58,7 +58,7 @@ build_backup_content(BackupState *state, bool ishistoryfile)
 
 	appendStringInfo(result, "CHECKPOINT LOCATION: %X/%X\n",
 					 LSN_FORMAT_ARGS(state->checkpointloc));
-	appendStringInfo(result, "BACKUP METHOD: streamed\n");
+	appendStringInfoString(result, "BACKUP METHOD: streamed\n");
 	appendStringInfo(result, "BACKUP FROM: %s\n",
 					 state->started_in_recovery ? "standby" : "primary");
 	appendStringInfo(result, "START TIME: %s\n", startstrbuf);
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index 3ded3c1473..7e5ec500d8 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -1282,7 +1282,7 @@ ReportSlotInvalidation(ReplicationSlotInvalidationCause cause,
 			break;
 
 		case RS_INVAL_WAL_LEVEL:
-			appendStringInfo(&err_detail, _("Logical decoding on standby requires wal_level >= logical on the primary server."));
+			appendStringInfoString(&err_detail, _("Logical decoding on standby requires wal_level >= logical on the primary server."));
 			break;
 		case RS_INVAL_NONE:
 			pg_unreachable();
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 8d5eac4791..442205382e 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -10395,7 +10395,7 @@ get_func_sql_syntax(FuncExpr *expr, deparse_context *context)
 
 		case F_IS_NORMALIZED:
 			/* IS xxx NORMALIZED */
-			appendStringInfoString(buf, "(");
+			appendStringInfoChar(buf, '(');
 			get_rule_expr_paren((Node *) linitial(expr->args), context, false,
 								(Node *) expr);
 			appendStringInfoString(buf, " IS");
@@ -10884,7 +10884,7 @@ get_json_constructor(JsonConstructorExpr *ctor, deparse_context *context,
 	}
 
 	get_json_constructor_options(ctor, buf);
-	appendStringInfo(buf, ")");
+	appendStringInfoChar(buf, ')');
 }
 
 /*
diff --git a/src/test/regress/pg_regress.c b/src/test/regress/pg_regress.c
index ec67588cf5..7f704da730 100644
--- a/src/test/regress/pg_regress.c
+++ b/src/test/regress/pg_regress.c
@@ -2339,9 +2339,9 @@ regression_main(int argc, char *argv[],
 							 bindir ? "/" : "",
 							 temp_instance);
 			if (debug)
-				appendStringInfo(&cmd, " --debug");
+				appendStringInfoString(&cmd, " --debug");
 			if (nolocale)
-				appendStringInfo(&cmd, " --no-locale");
+				appendStringInfoString(&cmd, " --no-locale");
 			appendStringInfo(&cmd, " > \"%s/log/initdb.log\" 2>&1", outputdir);
 			fflush(NULL);
 			if (system(cmd.data))