diff --git a/ibase_query.c b/ibase_query.c
index 052d97c5..57fe3c0b 100644
--- a/ibase_query.c
+++ b/ibase_query.c
@@ -796,7 +796,7 @@ static int _php_ibase_bind(ibase_query *ib_query, zval *b_vars) /* {{{ */
 		convert_to_string(b_var);
 		var->sqldata = Z_STRVAL_P(b_var);
 		var->sqllen = (ISC_SHORT)Z_STRLEN_P(b_var);
-		var->sqltype = SQL_TEXT; // Here: sqltype is modfied, can't rely on it for next calls
+		var->sqltype = SQL_TEXT | (var->sqltype & 1); // preserve nullable bit (issue #106)
 
 		// Another way to send string w/o converting base zval
 		// zend_string *str = zval_get_string(b_var);
diff --git a/tests/issue106_001.phpt b/tests/issue106_001.phpt
new file mode 100644
index 00000000..5cbe1d14
--- /dev/null
+++ b/tests/issue106_001.phpt
@@ -0,0 +1,50 @@
+--TEST--
+Issue #106: _php_ibase_bind() loses NULL flag when handling SQL_TEXT fallthrough
+--SKIPIF--
+<?php
+include("skipif.inc");
+?>
+--FILE--
+<?php
+
+require("interbase.inc");
+
+$db = ibase_connect($test_base);
+
+function test106() {
+	// Nullable VARCHAR column: the bind fallthrough path sets SQL_TEXT,
+	// which must preserve the nullable bit (sqltype & 1).
+	ibase_query('CREATE TABLE test106 (ID INTEGER, VAL VARCHAR(50))');
+	ibase_commit();
+
+	$insert = ibase_prepare('INSERT INTO test106 (ID, VAL) VALUES (?, ?)');
+
+	// First execute: non-null value triggers the SQL_TEXT fallthrough path
+	ibase_execute($insert, 1, 'hello');
+
+	// Second execute: NULL must be passed correctly;
+	// if the nullable bit was lost in the first call, this silently inserts
+	// the old value instead of NULL.
+	ibase_execute($insert, 2, null);
+
+	// Third execute: non-null again to verify the prepared statement still works
+	ibase_execute($insert, 3, 'world');
+
+	ibase_commit();
+
+	$res = ibase_query('SELECT ID, VAL FROM test106 ORDER BY ID');
+	while ($row = ibase_fetch_row($res)) {
+		$val = $row[1] === null ? 'NULL' : "'" . $row[1] . "'";
+		echo "ID={$row[0]} VAL=$val\n";
+	}
+	ibase_free_result($res);
+	ibase_free_query($insert);
+}
+
+test106();
+
+?>
+--EXPECT--
+ID=1 VAL='hello'
+ID=2 VAL=NULL
+ID=3 VAL='world'