diff --git a/driver/linker.cpp b/driver/linker.cpp
index 5a02bb157e..9c6d46ac1f 100644
--- a/driver/linker.cpp
+++ b/driver/linker.cpp
@@ -358,11 +358,16 @@ int executeMsvcToolAndWait(const std::string &tool,
      * be parsed properly.
      */
 
-    std::string cmdPath = getenv("ComSpec");
+    auto comspecEnv = getenv("ComSpec");
+    if (!comspecEnv) {
+      warning(Loc(), "'ComSpec' environment variable is not set, assuming 'cmd.exe'.");
+      comspecEnv = "cmd.exe";
+    }
+    std::string cmdExecutable = comspecEnv;
     std::string batchFile = exe_path::prependBinDir(
         global.params.targetTriple.isArch64Bit() ? "amd64.bat" : "x86.bat");
 
-    commandLine.append(windows::quoteArg(cmdPath));
+    commandLine.append(windows::quoteArg(cmdExecutable));
     commandLine.append(" /s /c \"");
     commandLine.append(windows::quoteArg(batchFile));
     commandLine.push_back(' ');