diff --git a/tests/tests-c-compiler/check-src/check-42.c b/tests/tests-c-compiler/check-src/check-42.c
index 8a59410..8d5868e 100644
--- a/tests/tests-c-compiler/check-src/check-42.c
+++ b/tests/tests-c-compiler/check-src/check-42.c
@@ -113,7 +113,8 @@
 
 	asn_fprint(stderr, &asn_DEF_LogLine, &ll);
 	buf_size = 128;
-	buf = alloca(buf_size);
+	uint8_t scratch[buf_size];
+	buf = scratch;
 	erval = der_encode(&asn_DEF_LogLine, &ll, buf_fill, 0);
 	assert(erval.encoded > 1);
 	fprintf(stderr, "Encoded in %zd bytes\n", erval.encoded);