diff --git a/tests/suites/test_suite_asn1write.data b/tests/suites/test_suite_asn1write.data
index c9b20d7..17f2067 100644
--- a/tests/suites/test_suite_asn1write.data
+++ b/tests/suites/test_suite_asn1write.data
@@ -30,3 +30,21 @@
 
 ASN.1 Write Octet String #9 (l = 128, buffer too small for string)
 asn1_write_octet_string:"000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F000102030405060708090A0B0C0D0E0F":"":127:POLARSSL_ERR_ASN1_BUF_TOO_SMALL
+
+ASN.1 Write IA5 String #0 (Empty string)
+asn1_write_ia5_string:"":"1600":2:2
+
+ASN.1 Write IA5 String #1 (Large buffer)
+asn1_write_ia5_string:"ABC":"1603414243":10:5
+
+ASN.1 Write IA5 String #2 (Buffer just fits)
+asn1_write_ia5_string:"ABC":"1603414243":5:5
+
+ASN.1 Write IA5 String #3 (Buffer too small for tag)
+asn1_write_ia5_string:"ABC":"":4:POLARSSL_ERR_ASN1_BUF_TOO_SMALL
+
+ASN.1 Write IA5 String #4 (Buffer too small for len)
+asn1_write_ia5_string:"ABC":"":3:POLARSSL_ERR_ASN1_BUF_TOO_SMALL
+
+ASN.1 Write IA5 String #5 (Buffer too small for string)
+asn1_write_ia5_string:"ABC":"":2:POLARSSL_ERR_ASN1_BUF_TOO_SMALL
diff --git a/tests/suites/test_suite_asn1write.function b/tests/suites/test_suite_asn1write.function
index 53cb739..72e9b4b 100644
--- a/tests/suites/test_suite_asn1write.function
+++ b/tests/suites/test_suite_asn1write.function
@@ -46,3 +46,39 @@
     }
 }
 /* END_CASE */
+
+/* BEGIN_CASE */
+void asn1_write_ia5_string( char *str, char *hex_asn1,
+                            int buf_len, int result )
+{
+    int ret;
+    unsigned char buf[150];
+    unsigned char asn1[150] = { 0 };
+    size_t str_len, asn1_len, i;
+    unsigned char *p;
+
+    memset( buf, GUARD_VAL, sizeof( buf ) );
+
+    str_len = strlen( str );
+    asn1_len = unhexify( asn1, hex_asn1 );
+
+    p = buf + GUARD_LEN + buf_len;
+
+    ret = asn1_write_ia5_string( &p, buf + GUARD_LEN, str, str_len );
+
+    /* Check for buffer overwrite on both sides */
+    for( i = 0; i < GUARD_LEN; i++ )
+    {
+        TEST_ASSERT( buf[i] == GUARD_VAL );
+        TEST_ASSERT( buf[GUARD_LEN + buf_len + i] == GUARD_VAL );
+    }
+
+    if( result >= 0 )
+    {
+        TEST_ASSERT( (size_t) ret == asn1_len );
+        TEST_ASSERT( p + asn1_len == buf + GUARD_LEN + buf_len );
+
+        TEST_ASSERT( memcmp( p, asn1, asn1_len ) == 0 );
+    }
+}
+/* END_CASE */