diff --git a/munix b/munix
index 649f1ba..eeb7f83 100755
--- a/munix
+++ b/munix
@@ -48,6 +48,16 @@ if [ "$MICROVM_CLOSURE" = "" ]; then
   exit 1
 fi
 
+if [ "$MUVM_PATH" = "" ]; then
+  echo "munix: muvm not found, provide a --muvm-bin-dir or fix \$PATH" >&2
+  exit 1
+fi
+
+if [ "$PASST_PATH" = "" ]; then
+  echo "munix: passt not found, provide a --passt-bin-dir or fix \$PATH" >&2
+  exit 1
+fi
+
 # Resolve symlinks automatically
 MICROVM_CLOSURE=$(realpath "$MICROVM_CLOSURE")