diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 359f8e02e..32254305e 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -1740,13 +1740,20 @@ void LocalDerivationGoal::runChild()
 
         bool setUser = true;
 
-        /* Make the contents of netrc available to builtin:fetchurl
-           (which may run under a different uid and/or in a sandbox). */
+        /* Make the contents of netrc and the CA certificate bundle
+           available to builtin:fetchurl (which may run under a
+           different uid and/or in a sandbox). */
         std::string netrcData;
-        try {
-            if (drv->isBuiltin() && drv->builder == "builtin:fetchurl")
-                netrcData = readFile(settings.netrcFile);
-        } catch (SysError &) { }
+        std::string caFileData;
+        if (drv->isBuiltin() && drv->builder == "builtin:fetchurl") {
+           try {
+               netrcData = readFile(settings.netrcFile);
+           } catch (SysError &) { }
+
+           try {
+               caFileData = readFile(settings.caFile);
+           } catch (SysError &) { }
+        }
 
 #if __linux__
         if (useChroot) {
@@ -2174,7 +2181,7 @@ void LocalDerivationGoal::runChild()
                     e.second = rewriteStrings(e.second, inputRewrites);
 
                 if (drv->builder == "builtin:fetchurl")
-                    builtinFetchurl(drv2, netrcData);
+                    builtinFetchurl(drv2, netrcData, caFileData);
                 else if (drv->builder == "builtin:buildenv")
                     builtinBuildenv(drv2);
                 else if (drv->builder == "builtin:unpack-channel")
diff --git a/src/libstore/builtins.hh b/src/libstore/builtins.hh
index d201fb3ac..3073179a5 100644
--- a/src/libstore/builtins.hh
+++ b/src/libstore/builtins.hh
@@ -6,7 +6,9 @@
 namespace nix {
 
 // TODO: make pluggable.
-void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData);
+void builtinFetchurl(const BasicDerivation & drv,
+    const std::string & netrcData,
+    const std::string & caFileData);
 void builtinUnpackChannel(const BasicDerivation & drv);
 
 }
diff --git a/src/libstore/builtins/fetchurl.cc b/src/libstore/builtins/fetchurl.cc
index 9e2f85503..7558ab494 100644
--- a/src/libstore/builtins/fetchurl.cc
+++ b/src/libstore/builtins/fetchurl.cc
@@ -6,7 +6,10 @@
 
 namespace nix {
 
-void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData)
+void builtinFetchurl(
+    const BasicDerivation & drv,
+    const std::string & netrcData,
+    const std::string & caFileData)
 {
     /* Make the host's netrc data available. Too bad curl requires
        this to be stored in a file. It would be nice if we could just
@@ -16,6 +19,9 @@ void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData)
         writeFile(settings.netrcFile, netrcData, 0600);
     }
 
+    settings.caFile = "ca-certificates.crt";
+    writeFile(settings.caFile, caFileData, 0600);
+
     auto getAttr = [&](const std::string & name) {
         auto i = drv.env.find(name);
         if (i == drv.env.end()) throw Error("attribute '%s' missing", name);