diff --git a/sdk/core/azure-core-test/src/main/java/com/azure/core/test/utils/TestProxyDownloader.java b/sdk/core/azure-core-test/src/main/java/com/azure/core/test/utils/TestProxyDownloader.java
index 90b22a1f64798..886b537bfbe2a 100644
--- a/sdk/core/azure-core-test/src/main/java/com/azure/core/test/utils/TestProxyDownloader.java
+++ b/sdk/core/azure-core-test/src/main/java/com/azure/core/test/utils/TestProxyDownloader.java
@@ -173,9 +173,11 @@ private static class PlatformInfo {
             } else if (osName.contains("linux")) {
                 platform = "linux";
                 extension = "tar.gz";
-            } else {
+            } else if (osName.contains("mac os x")) {
                 platform = "osx";
                 extension = "zip";
+            } else {
+                throw new RuntimeException("unexpected osName " + osName);
             }
             String arch = System.getProperty("os.arch").toLowerCase(Locale.ROOT);
             if (arch.contains("amd64")) {