diff --git a/src/bin/pg_basebackup/pg_createsubscriber.c b/src/bin/pg_basebackup/pg_createsubscriber.c
index 42aaa428aed..b92a978a426 100644
--- a/src/bin/pg_basebackup/pg_createsubscriber.c
+++ b/src/bin/pg_basebackup/pg_createsubscriber.c
@@ -1487,7 +1487,7 @@ start_standby_server(const struct CreateSubscriberOptions *opt, bool restricted_
 	appendPQExpBuffer(pg_ctl_cmd, " -s -o \"-c sync_replication_slots=off\"");
 
 	/* Prevent unintended slot invalidation */
-	appendPQExpBuffer(pg_ctl_cmd, " -o \"-c idle_replication_slot_timeout=0\"");
+	appendPQExpBufferStr(pg_ctl_cmd, " -o \"-c idle_replication_slot_timeout=0\"");
 
 	if (restricted_access)
 	{
@@ -1513,7 +1513,7 @@ start_standby_server(const struct CreateSubscriberOptions *opt, bool restricted_
 
 	/* Suppress to start logical replication if requested */
 	if (restrict_logical_worker)
-		appendPQExpBuffer(pg_ctl_cmd, " -o \"-c max_logical_replication_workers=0\"");
+		appendPQExpBufferStr(pg_ctl_cmd, " -o \"-c max_logical_replication_workers=0\"");
 
 	pg_log_debug("pg_ctl command is: %s", pg_ctl_cmd->data);
 	rc = system(pg_ctl_cmd->data);
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index b158d96a831..8ef9c6a021a 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -9751,7 +9751,7 @@ determineNotNullFlags(Archive *fout, PGresult *res, int r,
 		{
 			*invalidnotnulloids = createPQExpBuffer();
 			appendPQExpBufferChar(*invalidnotnulloids, '{');
-			appendPQExpBuffer(*invalidnotnulloids, "%s", constroid);
+			appendPQExpBufferStr(*invalidnotnulloids, constroid);
 		}
 		else
 			appendPQExpBuffer(*invalidnotnulloids, ",%s", constroid);
@@ -10978,7 +10978,7 @@ dumpRelationStats_dumper(Archive *fout, const void *userArg, const TocEntry *te)
 		 */
 		if (rsinfo->nindAttNames == 0)
 		{
-			appendPQExpBuffer(out, ",\n\t'attname', ");
+			appendPQExpBufferStr(out, ",\n\t'attname', ");
 			appendStringLiteralAH(out, attname, fout);
 		}
 		else
diff --git a/src/interfaces/libpq/fe-auth-oauth-curl.c b/src/interfaces/libpq/fe-auth-oauth-curl.c
index cd9c0323bb6..ddd87dcf02d 100644
--- a/src/interfaces/libpq/fe-auth-oauth-curl.c
+++ b/src/interfaces/libpq/fe-auth-oauth-curl.c
@@ -2859,7 +2859,7 @@ error_return:
 		}
 	}
 
-	appendPQExpBufferStr(&conn->errorMessage, "\n");
+	appendPQExpBufferChar(&conn->errorMessage, '\n');
 
 	return PGRES_POLLING_FAILED;
 }
diff --git a/src/test/modules/test_escape/test_escape.c b/src/test/modules/test_escape/test_escape.c
index f6b36448977..0b4883cc7c8 100644
--- a/src/test/modules/test_escape/test_escape.c
+++ b/src/test/modules/test_escape/test_escape.c
@@ -96,8 +96,7 @@ escape_literal(PGconn *conn, PQExpBuffer target,
 	escaped = PQescapeLiteral(conn, unescaped, unescaped_len);
 	if (!escaped)
 	{
-		appendPQExpBuffer(escape_err, "%s",
-						  PQerrorMessage(conn));
+		appendPQExpBufferStr(escape_err, PQerrorMessage(conn));
 		escape_err->data[escape_err->len - 1] = 0;
 		escape_err->len--;
 		return false;
@@ -120,8 +119,7 @@ escape_identifier(PGconn *conn, PQExpBuffer target,
 	escaped = PQescapeIdentifier(conn, unescaped, unescaped_len);
 	if (!escaped)
 	{
-		appendPQExpBuffer(escape_err, "%s",
-						  PQerrorMessage(conn));
+		appendPQExpBufferStr(escape_err, PQerrorMessage(conn));
 		escape_err->data[escape_err->len - 1] = 0;
 		escape_err->len--;
 		return false;
@@ -153,8 +151,7 @@ escape_string_conn(PGconn *conn, PQExpBuffer target,
 
 	if (error)
 	{
-		appendPQExpBuffer(escape_err, "%s",
-						  PQerrorMessage(conn));
+		appendPQExpBufferStr(escape_err, PQerrorMessage(conn));
 		escape_err->data[escape_err->len - 1] = 0;
 		escape_err->len--;
 		return false;
@@ -514,7 +511,7 @@ test_psql_parse(pe_test_config *tc, PQExpBuffer testname,
 						  "#\t\t %d: scan_result: %s prompt: %u, query_buf: ",
 						  matches, scan_res_s(scan_result), prompt_status);
 		escapify(details, query_buf->data, query_buf->len);
-		appendPQExpBuffer(details, "\n");
+		appendPQExpBufferChar(details, '\n');
 
 		matches++;
 	}
@@ -566,7 +563,7 @@ test_one_vector_escape(pe_test_config *tc, const pe_test_vector *tv, const pe_te
 	}
 
 	/* name to describe the test */
-	appendPQExpBuffer(testname, ">");
+	appendPQExpBufferChar(testname, '>');
 	escapify(testname, tv->escape, tv->escape_len);
 	appendPQExpBuffer(testname, "< - %s - %s",
 					  tv->client_encoding, ef->name);
@@ -575,7 +572,7 @@ test_one_vector_escape(pe_test_config *tc, const pe_test_vector *tv, const pe_te
 	appendPQExpBuffer(details, "#\t input: %zd bytes: ",
 					  tv->escape_len);
 	escapify(details, tv->escape, tv->escape_len);
-	appendPQExpBufferStr(details, "\n");
+	appendPQExpBufferChar(details, '\n');
 	appendPQExpBuffer(details, "#\t encoding: %s\n",
 					  tv->client_encoding);