diff --git a/include/polarssl/asn1write.h b/include/polarssl/asn1write.h
index 4659b24c1..808bf3abe 100644
--- a/include/polarssl/asn1write.h
+++ b/include/polarssl/asn1write.h
@@ -124,6 +124,18 @@ int asn1_write_oid( unsigned char **p, unsigned char *start, const char *oid );
 int asn1_write_algorithm_identifier( unsigned char **p, unsigned char *start,
                                      const char *oid );
 
+/**
+ * \brief           Write a boolean tag (ASN1_BOOLEAN) and value in ASN.1 format
+ *                  Note: function works backwards in data buffer
+ *
+ * \param p         reference to current position pointer
+ * \param start     start of the buffer (for bounds-checking)
+ * \param boolean   0 or 1
+ *
+ * \return          the length written or a negative error code
+ */
+int asn1_write_bool( unsigned char **p, unsigned char *start, int boolean );
+
 /**
  * \brief           Write an int tag (ASN1_INTEGER) and value in ASN.1 format
  *                  Note: function works backwards in data buffer
diff --git a/library/asn1write.c b/library/asn1write.c
index 463c730fb..893841f80 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -173,6 +173,23 @@ int asn1_write_algorithm_identifier( unsigned char **p, unsigned char *start,
     return( len );
 }
 
+int asn1_write_bool( unsigned char **p, unsigned char *start, int boolean )
+{
+    int ret;
+    size_t len = 0;
+
+    if( *p - start < 1 )
+        return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
+
+    *--(*p) = (boolean) ? 1 : 0;
+    len++;
+
+    ASN1_CHK_ADD( len, asn1_write_len( p, start, len ) );
+    ASN1_CHK_ADD( len, asn1_write_tag( p, start, ASN1_BOOLEAN ) );
+
+    return( len );
+}
+
 int asn1_write_int( unsigned char **p, unsigned char *start, int val )
 {
     int ret;