diff --git a/ext/pdo_firebird/firebird_driver.c b/ext/pdo_firebird/firebird_driver.c
index 6c2de01c85af6..40289719ce9e8 100644
--- a/ext/pdo_firebird/firebird_driver.c
+++ b/ext/pdo_firebird/firebird_driver.c
@@ -599,13 +599,13 @@ static void firebird_handle_closer(pdo_dbh_t *dbh) /* {{{ */
 	}
 
 	if (H->date_format) {
-		zend_string_release_ex(H->date_format, false);
+		pefree(H->date_format, dbh->is_persistent);
 	}
 	if (H->time_format) {
-		zend_string_release_ex(H->time_format, false);
+		pefree(H->time_format, dbh->is_persistent);
 	}
 	if (H->timestamp_format) {
-		zend_string_release_ex(H->timestamp_format, false);
+		pefree(H->timestamp_format, dbh->is_persistent);
 	}
 
 	if (H->einfo.errmsg) {
@@ -1091,9 +1091,11 @@ static bool pdo_firebird_set_attribute(pdo_dbh_t *dbh, zend_long attr, zval *val
 					return false;
 				}
 				if (H->date_format) {
-					zend_string_release_ex(H->date_format, false);
+					pefree(H->date_format, dbh->is_persistent);
+					H->date_format = NULL;
 				}
-				H->date_format = str;
+				H->date_format = pestrndup(ZSTR_VAL(str), ZSTR_LEN(str),dbh->is_persistent);
+				zend_string_release_ex(str, 0);
 			}
 			return true;
 
@@ -1104,9 +1106,11 @@ static bool pdo_firebird_set_attribute(pdo_dbh_t *dbh, zend_long attr, zval *val
 					return false;
 				}
 				if (H->time_format) {
-					zend_string_release_ex(H->time_format, false);
+					pefree(H->time_format, dbh->is_persistent);
+					H->time_format = NULL;
 				}
-				H->time_format = str;
+				H->time_format = pestrndup(ZSTR_VAL(str), ZSTR_LEN(str),dbh->is_persistent);
+				zend_string_release_ex(str, 0);
 			}
 			return true;
 
@@ -1117,9 +1121,11 @@ static bool pdo_firebird_set_attribute(pdo_dbh_t *dbh, zend_long attr, zval *val
 					return false;
 				}
 				if (H->timestamp_format) {
-					zend_string_release_ex(H->timestamp_format, false);
+					pefree(H->timestamp_format, dbh->is_persistent);
+					H->timestamp_format = NULL;
 				}
-				H->timestamp_format = str;
+				H->timestamp_format = pestrndup(ZSTR_VAL(str), ZSTR_LEN(str),dbh->is_persistent);
+				zend_string_release_ex(str, 0);
 			}
 			return true;
 
@@ -1240,27 +1246,15 @@ static int pdo_firebird_get_attribute(pdo_dbh_t *dbh, zend_long attr, zval *val)
 			return 1;
 
 		case PDO_FB_ATTR_DATE_FORMAT:
-			if (H->date_format) {
-				ZVAL_STR_COPY(val, H->date_format);
-			} else {
-				ZVAL_STRING(val, PDO_FB_DEF_DATE_FMT);
-			}
+			ZVAL_STRING(val, H->date_format ? H->date_format : PDO_FB_DEF_DATE_FMT);
 			return 1;
 
 		case PDO_FB_ATTR_TIME_FORMAT:
-			if (H->time_format) {
-				ZVAL_STR_COPY(val, H->time_format);
-			} else {
-				ZVAL_STRING(val, PDO_FB_DEF_TIME_FMT);
-			}
+			ZVAL_STRING(val, H->time_format ? H->time_format : PDO_FB_DEF_TIME_FMT);
 			return 1;
 
 		case PDO_FB_ATTR_TIMESTAMP_FORMAT:
-			if (H->timestamp_format) {
-				ZVAL_STR_COPY(val, H->timestamp_format);
-			} else {
-				ZVAL_STRING(val, PDO_FB_DEF_TIMESTAMP_FMT);
-			}
+			ZVAL_STRING(val, H->timestamp_format ? H->timestamp_format : PDO_FB_DEF_TIMESTAMP_FMT);
 			return 1;
 
 		case PDO_FB_TRANSACTION_ISOLATION_LEVEL:
diff --git a/ext/pdo_firebird/firebird_statement.c b/ext/pdo_firebird/firebird_statement.c
index 4310269314ce0..60a5e60e11bde 100644
--- a/ext/pdo_firebird/firebird_statement.c
+++ b/ext/pdo_firebird/firebird_statement.c
@@ -93,7 +93,7 @@ static int get_formatted_time_tz(pdo_stmt_t *stmt, const ISC_TIME_TZ* timeTz, zv
 	}
 	time = fb_encode_time(hours, minutes, seconds, fractions);
 	isc_decode_sql_time(&time, &t);
-	fmt = S->H->time_format ? ZSTR_VAL(S->H->time_format) : PDO_FB_DEF_TIME_FMT;
+	fmt = S->H->time_format ? S->H->time_format : PDO_FB_DEF_TIME_FMT;
 
 	size_t len = strftime(timeBuf, sizeof(timeBuf), fmt, &t);
 	if (len == 0) {
@@ -123,7 +123,7 @@ static int get_formatted_timestamp_tz(pdo_stmt_t *stmt, const ISC_TIMESTAMP_TZ*
 	ts.timestamp_time = fb_encode_time(hours, minutes, seconds, fractions);
 	isc_decode_timestamp(&ts, &t);
 
-	fmt = S->H->timestamp_format ? ZSTR_VAL(S->H->timestamp_format) : PDO_FB_DEF_TIMESTAMP_FMT;
+	fmt = S->H->timestamp_format ? S->H->timestamp_format : PDO_FB_DEF_TIMESTAMP_FMT;
 
 	size_t len = strftime(timestampBuf, sizeof(timestampBuf), fmt, &t);
 	if (len == 0) {
@@ -546,18 +546,18 @@ static int pdo_firebird_stmt_get_col(
 					break;
 				case SQL_TYPE_DATE:
 					isc_decode_sql_date((ISC_DATE*)var->sqldata, &t);
-					fmt = S->H->date_format ? ZSTR_VAL(S->H->date_format) : PDO_FB_DEF_DATE_FMT;
+					fmt = S->H->date_format ? S->H->date_format : PDO_FB_DEF_DATE_FMT;
 					if (0) {
 				case SQL_TYPE_TIME:
 						isc_decode_sql_time((ISC_TIME*)var->sqldata, &t);
-						fmt = S->H->time_format ? ZSTR_VAL(S->H->time_format) : PDO_FB_DEF_TIME_FMT;
+						fmt = S->H->time_format ? S->H->time_format : PDO_FB_DEF_TIME_FMT;
 					} else if (0) {
 				case SQL_TIMESTAMP:
 						{
 							ISC_TIMESTAMP timestamp = php_get_isc_timestamp_from_sqldata(var->sqldata);
 							isc_decode_timestamp(&timestamp, &t);
 						}
-						fmt = S->H->timestamp_format ? ZSTR_VAL(S->H->timestamp_format) : PDO_FB_DEF_TIMESTAMP_FMT;
+						fmt = S->H->timestamp_format ? S->H->timestamp_format : PDO_FB_DEF_TIMESTAMP_FMT;
 					}
 					/* convert the timestamp into a string */
 					char buf[80];
diff --git a/ext/pdo_firebird/php_pdo_firebird_int.h b/ext/pdo_firebird/php_pdo_firebird_int.h
index 1d58be1c4b717..a62c152ffab3e 100644
--- a/ext/pdo_firebird/php_pdo_firebird_int.h
+++ b/ext/pdo_firebird/php_pdo_firebird_int.h
@@ -73,9 +73,9 @@ typedef struct {
 	zend_ulong txn_isolation_level;
 
 	/* date and time format strings, can be set by the set_attribute method */
-	zend_string *date_format;
-	zend_string *time_format;
-	zend_string *timestamp_format;
+	char *date_format;
+	char *time_format;
+	char *timestamp_format;
 
 	unsigned sql_dialect:2;