diff --git a/src/include/ipxe/in.h b/src/include/ipxe/in.h
index a37784e2..0f19bbd7 100644
--- a/src/include/ipxe/in.h
+++ b/src/include/ipxe/in.h
@@ -50,6 +50,12 @@ struct in6_addr {
 #define s6_addr32       in6_u.u6_addr32
 };
 
+#define IN6_IS_ADDR_UNSPECIFIED( addr )					\
+	( ( ( ( ( const uint32_t * ) (addr) )[0] ) |			\
+	    ( ( ( const uint32_t * ) (addr) )[1] ) |			\
+	    ( ( ( const uint32_t * ) (addr) )[2] ) |			\
+	    ( ( ( const uint32_t * ) (addr) )[3] ) ) == 0 )
+
 #define IN6_IS_ADDR_MULTICAST( addr )					\
 	( *( ( const uint8_t * ) (addr) ) == 0xff )
 
diff --git a/src/net/ipv6.c b/src/net/ipv6.c
index 8279f058..abe993d0 100644
--- a/src/net/ipv6.c
+++ b/src/net/ipv6.c
@@ -399,7 +399,7 @@ static int ipv6_tx ( struct io_buffer *iobuf,
 		rc = -ENETUNREACH;
 		goto err;
 	}
-	if ( sin6_src )
+	if ( sin6_src && ! IN6_IS_ADDR_UNSPECIFIED ( &sin6_src->sin6_addr ) )
 		src = &sin6_src->sin6_addr;
 	memcpy ( &iphdr->src, src, sizeof ( iphdr->src ) );