diff --git a/simgear/io/HTTPClient.cxx b/simgear/io/HTTPClient.cxx
index fd8ec7e5..d00bcb91 100644
--- a/simgear/io/HTTPClient.cxx
+++ b/simgear/io/HTTPClient.cxx
@@ -107,6 +107,8 @@ public:
     unsigned int bytesTransferred;
     unsigned int lastTransferRate;
     uint64_t totalBytesDownloaded;
+
+    SGPath tlsCertificatePath;
 };
 
 Client::Client() :
@@ -122,6 +124,8 @@ Client::Client() :
     d->maxPipelineDepth = 5;
     setUserAgent("SimGear-" SG_STRINGIZE(SIMGEAR_VERSION));
 
+    d->tlsCertificatePath = SGPath::fromEnv("SIMGEAR_TLS_CERT_PATH");
+
     static bool didInitCurlGlobal = false;
     if (!didInitCurlGlobal) {
       curl_global_init(CURL_GLOBAL_ALL);
@@ -275,6 +279,11 @@ void Client::makeRequest(const Request_ptr& r)
 
     curl_easy_setopt(curlRequest, CURLOPT_FOLLOWLOCATION, 1);
 
+    if (!d->tlsCertificatePath.isNull()) {
+        const auto utf8 = d->tlsCertificatePath.utf8Str();
+        curl_easy_setopt(curlRequest, CURLOPT_CAINFO, utf8.c_str());
+    }
+
     if (!d->proxy.empty()) {
       curl_easy_setopt(curlRequest, CURLOPT_PROXY, d->proxy.c_str());
       curl_easy_setopt(curlRequest, CURLOPT_PROXYPORT, d->proxyPort);