diff --git a/templates/tools/dockerfile/csharp_deps.include b/templates/tools/dockerfile/csharp_deps.include
index 612b119e1c9..3a40711e372 100644
--- a/templates/tools/dockerfile/csharp_deps.include
+++ b/templates/tools/dockerfile/csharp_deps.include
@@ -2,8 +2,8 @@
 # C# dependencies
 
 # Update to a newer version of mono
-RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
-RUN echo "deb http://download.mono-project.com/repo/debian wheezy main" | tee /etc/apt/sources.list.d/mono-xamarin.list
+RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
+RUN echo "deb http://download.mono-project.com/repo/debian jessie main" | tee /etc/apt/sources.list.d/mono-official.list
 RUN echo "deb http://download.mono-project.com/repo/debian wheezy-apache24-compat main" | tee -a /etc/apt/sources.list.d/mono-xamarin.list
 RUN echo "deb http://download.mono-project.com/repo/debian wheezy-libjpeg62-compat main" | tee -a /etc/apt/sources.list.d/mono-xamarin.list
 
diff --git a/tools/dockerfile/interoptest/grpc_interop_csharp/Dockerfile b/tools/dockerfile/interoptest/grpc_interop_csharp/Dockerfile
index f9e709dccb1..90624e60105 100644
--- a/tools/dockerfile/interoptest/grpc_interop_csharp/Dockerfile
+++ b/tools/dockerfile/interoptest/grpc_interop_csharp/Dockerfile
@@ -82,8 +82,8 @@ RUN pip install futures==2.2.0 enum34==1.0.4 protobuf==3.2.0 six==1.10.0
 # C# dependencies
 
 # Update to a newer version of mono
-RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
-RUN echo "deb http://download.mono-project.com/repo/debian wheezy main" | tee /etc/apt/sources.list.d/mono-xamarin.list
+RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
+RUN echo "deb http://download.mono-project.com/repo/debian jessie main" | tee /etc/apt/sources.list.d/mono-official.list
 RUN echo "deb http://download.mono-project.com/repo/debian wheezy-apache24-compat main" | tee -a /etc/apt/sources.list.d/mono-xamarin.list
 RUN echo "deb http://download.mono-project.com/repo/debian wheezy-libjpeg62-compat main" | tee -a /etc/apt/sources.list.d/mono-xamarin.list
 
diff --git a/tools/dockerfile/interoptest/grpc_interop_csharpcoreclr/Dockerfile b/tools/dockerfile/interoptest/grpc_interop_csharpcoreclr/Dockerfile
index f9e709dccb1..90624e60105 100644
--- a/tools/dockerfile/interoptest/grpc_interop_csharpcoreclr/Dockerfile
+++ b/tools/dockerfile/interoptest/grpc_interop_csharpcoreclr/Dockerfile
@@ -82,8 +82,8 @@ RUN pip install futures==2.2.0 enum34==1.0.4 protobuf==3.2.0 six==1.10.0
 # C# dependencies
 
 # Update to a newer version of mono
-RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
-RUN echo "deb http://download.mono-project.com/repo/debian wheezy main" | tee /etc/apt/sources.list.d/mono-xamarin.list
+RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
+RUN echo "deb http://download.mono-project.com/repo/debian jessie main" | tee /etc/apt/sources.list.d/mono-official.list
 RUN echo "deb http://download.mono-project.com/repo/debian wheezy-apache24-compat main" | tee -a /etc/apt/sources.list.d/mono-xamarin.list
 RUN echo "deb http://download.mono-project.com/repo/debian wheezy-libjpeg62-compat main" | tee -a /etc/apt/sources.list.d/mono-xamarin.list
 
diff --git a/tools/dockerfile/test/csharp_coreclr_x64/Dockerfile b/tools/dockerfile/test/csharp_coreclr_x64/Dockerfile
index f9e709dccb1..90624e60105 100644
--- a/tools/dockerfile/test/csharp_coreclr_x64/Dockerfile
+++ b/tools/dockerfile/test/csharp_coreclr_x64/Dockerfile
@@ -82,8 +82,8 @@ RUN pip install futures==2.2.0 enum34==1.0.4 protobuf==3.2.0 six==1.10.0
 # C# dependencies
 
 # Update to a newer version of mono
-RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
-RUN echo "deb http://download.mono-project.com/repo/debian wheezy main" | tee /etc/apt/sources.list.d/mono-xamarin.list
+RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
+RUN echo "deb http://download.mono-project.com/repo/debian jessie main" | tee /etc/apt/sources.list.d/mono-official.list
 RUN echo "deb http://download.mono-project.com/repo/debian wheezy-apache24-compat main" | tee -a /etc/apt/sources.list.d/mono-xamarin.list
 RUN echo "deb http://download.mono-project.com/repo/debian wheezy-libjpeg62-compat main" | tee -a /etc/apt/sources.list.d/mono-xamarin.list
 
diff --git a/tools/dockerfile/test/csharp_jessie_x64/Dockerfile b/tools/dockerfile/test/csharp_jessie_x64/Dockerfile
index 0b21a222263..7c2a2df30c4 100644
--- a/tools/dockerfile/test/csharp_jessie_x64/Dockerfile
+++ b/tools/dockerfile/test/csharp_jessie_x64/Dockerfile
@@ -86,8 +86,8 @@ RUN pip install futures==2.2.0 enum34==1.0.4 protobuf==3.2.0 six==1.10.0
 # C# dependencies
 
 # Update to a newer version of mono
-RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
-RUN echo "deb http://download.mono-project.com/repo/debian wheezy main" | tee /etc/apt/sources.list.d/mono-xamarin.list
+RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
+RUN echo "deb http://download.mono-project.com/repo/debian jessie main" | tee /etc/apt/sources.list.d/mono-official.list
 RUN echo "deb http://download.mono-project.com/repo/debian wheezy-apache24-compat main" | tee -a /etc/apt/sources.list.d/mono-xamarin.list
 RUN echo "deb http://download.mono-project.com/repo/debian wheezy-libjpeg62-compat main" | tee -a /etc/apt/sources.list.d/mono-xamarin.list
 
diff --git a/tools/dockerfile/test/multilang_jessie_x64/Dockerfile b/tools/dockerfile/test/multilang_jessie_x64/Dockerfile
index 9b50d85e2f3..d85411810d7 100644
--- a/tools/dockerfile/test/multilang_jessie_x64/Dockerfile
+++ b/tools/dockerfile/test/multilang_jessie_x64/Dockerfile
@@ -71,8 +71,8 @@ RUN pip install --upgrade google-api-python-client
 # C# dependencies
 
 # Update to a newer version of mono
-RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
-RUN echo "deb http://download.mono-project.com/repo/debian wheezy main" | tee /etc/apt/sources.list.d/mono-xamarin.list
+RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
+RUN echo "deb http://download.mono-project.com/repo/debian jessie main" | tee /etc/apt/sources.list.d/mono-official.list
 RUN echo "deb http://download.mono-project.com/repo/debian wheezy-apache24-compat main" | tee -a /etc/apt/sources.list.d/mono-xamarin.list
 RUN echo "deb http://download.mono-project.com/repo/debian wheezy-libjpeg62-compat main" | tee -a /etc/apt/sources.list.d/mono-xamarin.list