diff --git a/src/check.c b/src/check.c
index 54704bd..b036bba 100644
--- a/src/check.c
+++ b/src/check.c
@@ -832,7 +832,9 @@
 					chunk_appendf(chk, " (expect string '%.*s')", (unsigned int)istlen(expect->data), istptr(expect->data));
 					break;
 				case TCPCHK_EXPECT_BINARY:
-					chunk_appendf(chk, " (expect binary '%.*s')", (unsigned int)istlen(expect->data), istptr(expect->data));
+					chunk_appendf(chk, " (expect binary '");
+					dump_binary(chk, istptr(expect->data), (int)istlen(expect->data));
+					chunk_appendf(chk, "')");
 					break;
 				case TCPCHK_EXPECT_STRING_REGEX:
 					chunk_appendf(chk, " (expect regex)");