diff --git a/src/lsi/vm.c b/src/lsi/vm.c
index 9175fac..ead936a 100644
--- a/src/lsi/vm.c
+++ b/src/lsi/vm.c
@@ -861,7 +861,9 @@ void vm_load_file(char *filename)
 	char *ptr;
 
 	fh = fopen(filename, "r");
-	assert(fh != NULL);
+	if (fh == NULL) {
+		err(1, "Failed to open '%s'", filename);
+	}
 
 	for (ptr = vm_codearea; ptr < vm_codearea+vm_codesize; ptr++) {
 		int c;
@@ -887,16 +889,19 @@ void vm_init_functions(void)
 	struct hashentry *ptr;
 
 	/* First, let's check the magic */
-	assert(vm_codearea[0] == MAGIC1);
-	assert(vm_codearea[1] == MAGIC2);
-	assert(vm_codearea[2] == VERSION1);
-	assert(vm_codearea[3] == VERSION2);
-
-	assert(GETINT(vm_codearea, 8) == vm_abiversion1);
-	assert(GETINT(vm_codearea, 12) == vm_abiversion2);
-	assert(GETINT(vm_codearea, 16) == vm_abiversion3);
-	assert(GETINT(vm_codearea, 20) == vm_abiversion4);
-	assert(GETINT(vm_codearea, 24) == vm_abiversion5);
+	if ((vm_codearea[0] != MAGIC1) ||
+	    (vm_codearea[1] != MAGIC2))
+		errx(1, "Bad magic - not a lightscript binary");
+	if ((vm_codearea[2] != VERSION1) ||
+	    (vm_codearea[3] != VERSION2))
+		errx(1, "Bad version - recompile");
+
+	if ((GETINT(vm_codearea, 8) != vm_abiversion1) ||
+	    (GETINT(vm_codearea, 12) == vm_abiversion2) ||
+	    (GETINT(vm_codearea, 16) == vm_abiversion3) ||
+	    (GETINT(vm_codearea, 20) == vm_abiversion4) ||
+	    (GETINT(vm_codearea, 24) == vm_abiversion5))
+		errx(1, "Incompatible ABI version - recompile");
 
 	/* Now, get the function table pointer */
 	t = GETINT(vm_codearea, 4);