diff --git a/external/CMakeLists.txt b/external/CMakeLists.txt
index d4091a854..9634f0036 100644
--- a/external/CMakeLists.txt
+++ b/external/CMakeLists.txt
@@ -76,5 +76,10 @@ target_include_directories(cpr PUBLIC cpr/include)
 target_compile_definitions(cpr PUBLIC CPR_CURL_NOSIGNAL)
 add_library(cpr::cpr ALIAS cpr)
 
+# We don't need any of these as we don't use the ssl crypto helper code at all:
+set(ENABLE_GNUTLS OFF CACHE BOOL "Disable gnutls for ngtcp2")
+set(ENABLE_OPENSSL OFF CACHE BOOL "Disable openssl for ngtcp2")
+set(ENABLE_BORINGSSL OFF CACHE BOOL "Disable boringssl for ngtcp2")
+
 add_definitions(-D_GNU_SOURCE)
 add_subdirectory(ngtcp2 EXCLUDE_FROM_ALL)