diff --git a/build.sh b/build.sh
index 430a533f9e..775200a963 100755
--- a/build.sh
+++ b/build.sh
@@ -316,7 +316,10 @@ restore=true
 
 InitializeToolset
 
-InstallDotNetSdk "$repo_root/.dotnet" "3.1.102-servicing-014873"
+dotnet_install_dir="$repo_root/.dotnet"
+if [[ ! -d "$dotnet_install_dir/sdk/3.1.102" ]]; then
+    InstallDotNetSdk "$dotnet_install_dir" "3.1.102-servicing-014873"
+fi
 
 restore=$_tmp_restore=