diff --git a/lib/dns/resolver.c b/lib/dns/resolver.c
index 99c4486868..bf0eab36b7 100644
--- a/lib/dns/resolver.c
+++ b/lib/dns/resolver.c
@@ -4936,9 +4936,10 @@ fctx_create(dns_resolver_t *res, const dns_name_t *name, dns_rdatatype_t type,
 	isc_result_t iresult;
 	isc_interval_t interval;
 	unsigned int findoptions = 0;
-	char buf[DNS_NAME_FORMATSIZE + DNS_RDATATYPE_FORMATSIZE];
+	char buf[DNS_NAME_FORMATSIZE + DNS_RDATATYPE_FORMATSIZE + 1];
 	char typebuf[DNS_RDATATYPE_FORMATSIZE];
 	isc_mem_t *mctx;
+	size_t p;
 
 	/*
 	 * Caller must be holding the lock for bucket number 'bucketnum'.
@@ -4965,8 +4966,8 @@ fctx_create(dns_resolver_t *res, const dns_name_t *name, dns_rdatatype_t type,
 	 */
 	dns_name_format(name, buf, sizeof(buf));
 	dns_rdatatype_format(type, typebuf, sizeof(typebuf));
-	strlcat(buf, "/", sizeof(buf));
-	strlcat(buf, typebuf, sizeof(buf));
+	p = strlcat(buf, "/", sizeof(buf));
+	strlcat(buf + p, typebuf, sizeof(buf));
 	fctx->info = isc_mem_strdup(mctx, buf);
 
 	FCTXTRACE("create");