diff --git a/pkgs/applications/networking/mailreaders/imapfilter.nix b/pkgs/applications/networking/mailreaders/imapfilter.nix
index fad018011ba..b677d82dce4 100644
--- a/pkgs/applications/networking/mailreaders/imapfilter.nix
+++ b/pkgs/applications/networking/mailreaders/imapfilter.nix
@@ -10,8 +10,11 @@ stdenv.mkDerivation rec {
     rev = "v${version}";
     sha256 = "0f65sg6hhv6778fxwsz4hvarbm97dsb8jj0mg7a9qs273r35pqck";
   };
+  makeFlags = [
+    "SSLCAFILE=/etc/ssl/certs/ca-bundle.crt"
+    "PREFIX=$(out)"
+  ];
 
-  makeFlagsArray = "PREFIX=$(out)";
   propagatedBuildInputs = [ openssl pcre lua ];
 
   meta = {