diff --git a/extra/firefox/build b/extra/firefox/build
index 6d9c0a25..7f3506a2 100755
--- a/extra/firefox/build
+++ b/extra/firefox/build
@@ -6,14 +6,27 @@
     cd autoconf2.13
 
     ./configure \
-        --prefix="$PWD/../autoconf" \
+        --prefix="$PWD/../junk" \
         --program-suffix=-2.13
 
     make
     make install
 )
 
-export PATH=$PWD/autoconf/bin:$PATH
+# Build yasm for Firefox's sole use.
+# Firefox is the only package which needs it
+# and upstream is kinda dead.
+(
+    cd yasm
+
+    ./configure \
+        --prefix="$PWD/../junk"
+
+    make
+    make install
+)
+
+export PATH=$PWD/junk/bin:$PATH
 export LDFLAGS="$LDFLAGS -Wl,-rpath=/usr/lib/firefox"
 export CC=${CC:-gcc}
 export CXX=${CXX:-g++}
diff --git a/extra/firefox/checksums b/extra/firefox/checksums
index be8e2b9d..e7f760f9 100644
--- a/extra/firefox/checksums
+++ b/extra/firefox/checksums
@@ -1,5 +1,6 @@
 52e784f98a37624e8b207f1b23289c2c88f66dd923798cae891a586a6d94a6d1  firefox-68.5.0esr.source.tar.xz
 f0611136bee505811e9ca11ca7ac188ef5323a8e2ef19cffd3edb3cf08fd791e  autoconf-2.13.tar.gz
+3dce6601b495f5b3d45b59f7d2492a340ee7e84b5beca17e48f862502bd5603f  yasm-1.3.0.tar.gz
 b5e70b12cc9dd18fffd7924a7d3a2e11574136fe0764359d08eba0755f1c5d4c  mozconfig
 960d82bbfdc88c95f5cb4f2e1c1bf23dae7519b3b7203914d7b3ddbff1ba4c28  stab.h
 315880530f09175788dfa48a1915bfa1e190bfd3e267988b9100cb93006c808c  fix-fortify-system-wrappers.patch
diff --git a/extra/firefox/depends b/extra/firefox/depends
index d9a42ce7..c62eca2d 100644
--- a/extra/firefox/depends
+++ b/extra/firefox/depends
@@ -47,6 +47,5 @@ pixman
 python        make
 python2       make
 rust          make
-yasm          make
 zip           make
 zlib
diff --git a/extra/firefox/sources b/extra/firefox/sources
index 061a07f3..d9679fd2 100644
--- a/extra/firefox/sources
+++ b/extra/firefox/sources
@@ -1,5 +1,6 @@
 https://ftp.mozilla.org/pub/firefox/releases/68.5.0esr/source/firefox-68.5.0esr.source.tar.xz
 https://ftp.gnu.org/gnu/autoconf/autoconf-2.13.tar.gz autoconf2.13/
+https://www.tortall.net/projects/yasm/releases/yasm-1.3.0.tar.gz yasm/
 files/mozconfig
 files/stab.h toolkit/crashreporter/google-breakpad/src/
 patches/fix-fortify-system-wrappers.patch