diff --git a/pkgs/applications/networking/irc/weechat/scripts/weechat-matrix-bridge/default.nix b/pkgs/applications/networking/irc/weechat/scripts/weechat-matrix-bridge/default.nix
index 137a32f9364f..233fe418df3a 100644
--- a/pkgs/applications/networking/irc/weechat/scripts/weechat-matrix-bridge/default.nix
+++ b/pkgs/applications/networking/irc/weechat/scripts/weechat-matrix-bridge/default.nix
@@ -42,5 +42,9 @@ stdenv.mkDerivation {
     maintainers = with maintainers; [ ma27 ];
     license = licenses.mit; # see https://github.com/torhve/weechat-matrix-protocol-script/blob/0052e7275ae149dc5241226391c9b1889ecc3c6b/matrix.lua#L53
     platforms = platforms.unix;
+
+    # As of 2019-06-30, all of the dependencies are available on macOS but the
+    # package itself does not build.
+    broken = stdenv.isDarwin;
   };
 }
diff --git a/pkgs/development/libraries/mtxclient/default.nix b/pkgs/development/libraries/mtxclient/default.nix
index ee8c8f101a24..ef8525cf54d7 100644
--- a/pkgs/development/libraries/mtxclient/default.nix
+++ b/pkgs/development/libraries/mtxclient/default.nix
@@ -27,5 +27,9 @@ stdenv.mkDerivation rec {
     license = licenses.mit;
     maintainers = with maintainers; [ fpletz ];
     platforms = platforms.unix;
+
+    # As of 2019-06-30, all of the dependencies are available on macOS but the
+    # package itself does not build.
+    broken = stdenv.isDarwin;
   };
 }
diff --git a/pkgs/development/libraries/olm/default.nix b/pkgs/development/libraries/olm/default.nix
index 4749efb5f006..49daff30e7b5 100644
--- a/pkgs/development/libraries/olm/default.nix
+++ b/pkgs/development/libraries/olm/default.nix
@@ -8,7 +8,7 @@ stdenv.mkDerivation rec {
     description = "Implements double cryptographic ratchet and Megolm ratchet";
     license = stdenv.lib.licenses.asl20;
     homepage = https://matrix.org/git/olm/about;
-    platforms = stdenv.lib.platforms.linux;
+    platforms = with stdenv.lib.platforms; darwin ++ linux;
   };
 
   src = fetchurl {
@@ -22,5 +22,7 @@ stdenv.mkDerivation rec {
   # requires optimisation but memory operations are compiled with -O0
   hardeningDisable = ["fortify"];
 
+  makeFlags = if stdenv.cc.isClang then [ "CC=cc" ] else null;
+
   installFlags = "PREFIX=$(out)";
 }