diff --git a/scripts/crosstool-NG.sh.in b/scripts/crosstool-NG.sh.in
index d4e15fe3..b42b187b 100644
--- a/scripts/crosstool-NG.sh.in
+++ b/scripts/crosstool-NG.sh.in
@@ -134,6 +134,9 @@ CT_DoBuildTargetTuple
 # then rescan the options file now:
 . .config
 
+# Sanity check some directories
+CT_TestAndAbort "'CT_PREFIX_DIR' is not set: where should I install?" -z "${CT_PREFIX_DIR}"
+
 # Second kludge: merge user-supplied target CFLAGS with architecture-provided
 # target CFLAGS. Do the same for LDFLAGS in case it happens in the future.
 # Put user-supplied flags at the end, so that they take precedence.