diff --git usr.bin/m4/eval.c usr.bin/m4/eval.c
index fbd42aa..cc052b7 100644
--- usr.bin/m4/eval.c
+++ usr.bin/m4/eval.c
@@ -688,7 +688,8 @@ dotrace(const char *argv[], int argc, int on)
 static void
 doifelse(const char *argv[], int argc)
 {
-	cycle {
+	/* Need at least 5 elements to safely evaluate expressions. */
+	while (argc > 4) {
 		if (STREQ(argv[2], argv[3]))
 			pbstr(argv[4]);
 		else if (argc == 6)