diff --git a/ext/pdo/pdo_dbh.c b/ext/pdo/pdo_dbh.c
index 47c9072da56..6a8bea5068b 100644
--- a/ext/pdo/pdo_dbh.c
+++ b/ext/pdo/pdo_dbh.c
@@ -1164,7 +1164,7 @@ PHP_METHOD(PDO, query)
 PHP_METHOD(PDO, quote)
 {
 	pdo_dbh_t *dbh = Z_PDO_DBH_P(ZEND_THIS);
-	zend_string *str;
+	zend_string *str, *quoted;
 	zend_long paramtype = PDO_PARAM_STR;
 
 	ZEND_PARSE_PARAMETERS_START(1, 2)
@@ -1180,8 +1180,14 @@ PHP_METHOD(PDO, quote)
 		pdo_raise_impl_error(dbh, NULL, "IM001", "driver does not support quoting");
 		RETURN_FALSE;
 	}
+	quoted = dbh->methods->quoter(dbh, str, paramtype);
 
-	RETURN_STR(dbh->methods->quoter(dbh, str, paramtype));
+	if (quoted == NULL) {
+		PDO_HANDLE_DBH_ERR();
+		RETURN_FALSE;
+	}
+
+	RETURN_STR(quoted);
 }
 /* }}} */
 
diff --git a/ext/pdo/pdo_sql_parser.re b/ext/pdo/pdo_sql_parser.re
index 4c207003797..6bb0837fb31 100644
--- a/ext/pdo/pdo_sql_parser.re
+++ b/ext/pdo/pdo_sql_parser.re
@@ -242,6 +242,13 @@ safe:
 						if (buf) {
 							zend_string_release_ex(buf, 0);
 						}
+						if (plc->quoted == NULL) {
+							/* bork */
+							ret = -1;
+							strncpy(stmt->error_code, stmt->dbh->error_code, 6);
+							goto clean_up;
+						}
+
 					} else {
 						pdo_raise_impl_error(stmt->dbh, stmt, "HY105", "Expected a stream resource");
 						ret = -1;
diff --git a/ext/pdo_sqlite/sqlite_driver.c b/ext/pdo_sqlite/sqlite_driver.c
index 6a41e2162a9..de5170a35a9 100644
--- a/ext/pdo_sqlite/sqlite_driver.c
+++ b/ext/pdo_sqlite/sqlite_driver.c
@@ -226,7 +226,11 @@ static zend_string *pdo_sqlite_last_insert_id(pdo_dbh_t *dbh, const zend_string
 /* NB: doesn't handle binary strings... use prepared stmts for that */
 static zend_string* sqlite_handle_quoter(pdo_dbh_t *dbh, const zend_string *unquoted, enum pdo_param_type paramtype)
 {
-	char *quoted = safe_emalloc(2, ZSTR_LEN(unquoted), 3);
+	char *quoted;
+	if (ZSTR_LEN(unquoted) > (INT_MAX - 3) / 2) {
+		return NULL;
+	}
+	quoted = safe_emalloc(2, ZSTR_LEN(unquoted), 3);
 	/* TODO use %Q format? */
 	sqlite3_snprintf(2*ZSTR_LEN(unquoted) + 3, quoted, "'%q'", ZSTR_VAL(unquoted));
 	zend_string *quoted_str = zend_string_init(quoted, strlen(quoted), 0);
diff --git a/ext/pdo_sqlite/tests/bug81740.phpt b/ext/pdo_sqlite/tests/bug81740.phpt
new file mode 100644
index 00000000000..99fb07c3048
--- /dev/null
+++ b/ext/pdo_sqlite/tests/bug81740.phpt
@@ -0,0 +1,17 @@
+--TEST--
+Bug #81740 (PDO::quote() may return unquoted string)
+--SKIPIF--
+<?php
+if (!extension_loaded('pdo_sqlite')) print 'skip not loaded';
+if (getenv("SKIP_SLOW_TESTS")) die("skip slow test");
+?>
+--INI--
+memory_limit=-1
+--FILE--
+<?php
+$pdo = new PDO("sqlite::memory:");
+$string = str_repeat("a", 0x80000000);
+var_dump($pdo->quote($string));
+?>
+--EXPECT--
+bool(false)