diff --git a/content/canvas/src/dummy.cpp b/content/canvas/src/dummy.cpp
index 7e06bf6b6db7..582c5135ea3a 100644
--- a/content/canvas/src/dummy.cpp
+++ b/content/canvas/src/dummy.cpp
@@ -1,4 +1,8 @@
 /*
  * This file only exists because some platforms can't handle building an empty .a
  * file, or .lib, or whatever (e.g. OS X, possibly Win32).
+ *
+ * Need at least one external symbol for some linkers to create a proper
+ * archive file: https://bugzilla.mozilla.org/show_bug.cgi?id=311143
  */
+void concvsdummy(void) {}