diff --git a/var/spack/repos/builtin/packages/dotnet-core-sdk/package.py b/var/spack/repos/builtin/packages/dotnet-core-sdk/package.py
index 723d5021413..6f74fe3d5dc 100644
--- a/var/spack/repos/builtin/packages/dotnet-core-sdk/package.py
+++ b/var/spack/repos/builtin/packages/dotnet-core-sdk/package.py
@@ -86,9 +86,9 @@ class DotnetCoreSdk(Package):
 
     variant("telemetry", default=False, description="allow collection of telemetry data")
 
-    def setup_build_environment(self, env):
-        if "-telemetry" in self.spec:
-            env.set("DOTNET_CLI_TELEMETRY_OPTOUT", 1)
+    def setup_run_environment(self, env):
+        if "~telemetry" in self.spec:
+            env.set("DOTNET_CLI_TELEMETRY_OPTOUT", "1")
 
     def install(self, spec, prefix):
         mkdirp("bin")