diff '--color=auto' -aur a/src/fr-command-zip.c b/src/fr-command-zip.c
--- a/src/fr-command-zip.c	2017-03-13 05:45:12.000000000 -0700
+++ b/src/fr-command-zip.c	2017-03-17 16:13:39.116752773 -0700
@@ -385,6 +385,7 @@
 				"application/x-ear",
 				"application/x-ms-dos-executable",
 				"application/x-war",
+				"application/x-xpinstall",
 				"application/zip",
 				NULL };
 
diff '--color=auto' -aur a/src/fr-init.c b/src/fr-init.c
--- a/src/fr-init.c	2017-03-17 16:08:13.736744000 -0700
+++ b/src/fr-init.c	2017-03-17 16:15:15.546755263 -0700
@@ -97,6 +97,7 @@
 	{ "application/x-tarz",                 ".tar.Z",    N_("Tar compressed with compress (.tar.Z)"), 0 },
 	{ "application/x-stuffit",              ".sit",      NULL, 0 },
 	{ "application/x-war",                  ".war",      N_("War (.war)"), 0 },
+	{ "application/x-xpinstall",            ".xpi",      N_("Firefox Addon Installer (.xpi)"), 0 },
 	{ "application/x-xz",                   ".xz",       N_("Xz (.xz)"), 0 },
 	{ "application/x-xz-compressed-tar",    ".tar.xz",   N_("Tar compressed with xz (.tar.xz)"), 0 },
 	{ "application/x-zoo",                  ".zoo",      N_("Zoo (.zoo)"), 0 },
@@ -155,6 +156,7 @@
 	{ ".tzo", "application/x-lzop-compressed-tar" },
 	{ ".war", "application/x-war" },
 	{ ".wim", "application/x-ms-wim" },
+	{ ".xpi", "application/x-xpinstall" },
 	{ ".xz", "application/x-xz" },
 	{ ".z", "application/x-gzip" },
 	{ ".Z", "application/x-compress" },