diff --git a/steps/zlib-1.2.13/pass1.sh b/steps/zlib-1.2.13/pass1.sh
index ab87fc74..36c86a5e 100755
--- a/steps/zlib-1.2.13/pass1.sh
+++ b/steps/zlib-1.2.13/pass1.sh
@@ -2,6 +2,30 @@
 #
 # SPDX-License-Identifier: GPL-3.0-or-later
 
+src_prepare() {
+    default
+
+    rm zlib.3.pdf \
+        doc/crc-doc.1.0.pdf \
+        contrib/puff/zeros.raw \
+        contrib/blast/test.pk \
+        contrib/dotzlib/DotZLib.chm
+
+    rm crc32.h
+    gcc -DMAKECRCH crc32.c -o gen_crc32h
+    ./gen_crc32h
+
+    echo "void makefixed(void); int main() { makefixed(); }" > makefixed_main.c
+    gcc -DMAKEFIXED inflate.c crc32.c zutil.c inftrees.c \
+        adler32.c inffast.c makefixed_main.c -o gen_inffixedh
+    ./gen_inffixedh > inffixed.h
+
+    echo "void makefixed9(void); int main() { makefixed9(); }" > makefixed9_main.c
+    gcc -DMAKEFIXED -I. contrib/infback9/infback9.c zutil.c \
+        contrib/infback9/inftree9.c makefixed9_main.c -o gen_inffix9h
+    ./gen_inffix9h > contrib/infback9/inffix9.h
+}
+
 src_configure() {
     ./configure --prefix="${PREFIX}" --libdir="${LIBDIR}" --static
 }