diff --git a/package/rtty/0001-src-CMakeLists.txt-fix-build-with-mbedtls-but-withou.patch b/package/rtty/0001-src-CMakeLists.txt-fix-build-with-mbedtls-but-withou.patch
new file mode 100644
index 0000000000..b7275462af
--- /dev/null
+++ b/package/rtty/0001-src-CMakeLists.txt-fix-build-with-mbedtls-but-withou.patch
@@ -0,0 +1,47 @@
+From 0982308255dd3fd70e7b93aa88a8f3c5b9c1b845 Mon Sep 17 00:00:00 2001
+From: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+Date: Sun, 30 Aug 2020 21:15:06 +0200
+Subject: [PATCH] src/CMakeLists.txt: fix build with mbedtls but without zlib
+
+Building with mbedtls but without zlib will result in the following
+build failure:
+
+-- Found MbedTLS: /home/peko/autobuild/instance-0/output-1/per-package/rtty/host/powerpc64-buildroot-linux-gnu/sysroot/usr/lib/libmbedtls.so (found version "2.16.7")
+-- Could NOT find ZLIB (missing: ZLIB_LIBRARY ZLIB_INCLUDE_DIR)
+-- Select MbedTLS(PolarSSL) as the SSL backend
+CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
+Please set them or make sure they are set and tested correctly in the CMake files:
+ZLIB_LIBRARY
+    linked by target "rtty" in directory /home/peko/autobuild/instance-0/output-1/build/rtty-7.1.4/src
+
+-- Configuring incomplete, errors occurred!
+
+Fixes:
+ - http://autobuild.buildroot.org/results/a0ebffe58bbf14cab74b7d2111d4d88a9c725273
+
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+[Upstream status: https://github.com/zhaojh329/rtty/pull/77]
+---
+ src/CMakeLists.txt | 6 +++++-
+ 1 file changed, 5 insertions(+), 1 deletion(-)
+
+diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
+index 10f6626..d09e848 100644
+--- a/src/CMakeLists.txt
++++ b/src/CMakeLists.txt
+@@ -77,7 +77,11 @@ else()
+     elseif(RTTY_USE_MBEDTLS)
+         set(SSL_NAME "MbedTLS(PolarSSL)")
+         set(SSL_INC ${MBEDTLS_INCLUDE_DIR})
+-        set(SSL_LIB ${MBEDTLS_LIBRARIES} ${ZLIB_LIBRARIES})
++        if(ZLIB_FOUND)
++            set(SSL_LIB ${MBEDTLS_LIBRARIES} ${ZLIB_LIBRARIES})
++        else()
++            set(SSL_LIB ${MBEDTLS_LIBRARIES}) 
++        endif()
+         set(RTTY_HAVE_MBEDTLS_CONFIG 1)
+     endif()
+ 
+-- 
+2.28.0
+