diff --git a/.travis.yml b/.travis.yml
index 01543aa..8865483 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -270,7 +270,8 @@ matrix:
             - clang-9
           sources:
             - ubuntu-toolchain-r-test
-            - llvm-toolchain-xenial-9
+            - sourceline: 'deb https://apt.llvm.org/xenial/ llvm-toolchain-xenial-9 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
 
     - os: linux
       compiler: clang++-10
@@ -281,7 +282,8 @@ matrix:
             - clang-10
           sources:
             - ubuntu-toolchain-r-test
-            - llvm-toolchain-xenial-10
+            - sourceline: 'deb https://apt.llvm.org/xenial/ llvm-toolchain-xenial-10 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
 
     - os: linux
       dist: trusty