diff --git a/dom/media/webspeech/moz.build b/dom/media/webspeech/moz.build
index 677e0656f6..c61c63b720 100644
--- a/dom/media/webspeech/moz.build
+++ b/dom/media/webspeech/moz.build
@@ -3,5 +3,11 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
+# Due to IPC entanglement we always need the synthesis ipdls
 if CONFIG['MOZ_WEBSPEECH']:
     DIRS += ['synth']
+else:
+    IPDL_SOURCES += [
+        'synth/ipc/PSpeechSynthesis.ipdl',
+        'synth/ipc/PSpeechSynthesisRequest.ipdl',
+    ]
\ No newline at end of file