diff --git a/configure b/configure
index 43881cd12f87b74da63d56374be322c029d411c6..f8054cffbb6ae27d54577c05adb95dea2bef3ad5 100755
--- a/configure
+++ b/configure
@@ -1563,7 +1563,7 @@ case $target_os in
         ;;
 
     *)
-        target_os="${target_os}-UNKNOWN"
+        die "Unknown OS '$target_os'."
         ;;
 esac