diff --git a/build.sh b/build.sh
index 6ae7190..89f52fb 100755
--- a/build.sh
+++ b/build.sh
@@ -27,8 +27,8 @@ fi
 
 mkdir -p build
 
-$CLANG $CFLAGS -Ijni-headers -fuse-ld=lld oc2rnet.c -shared -target x86_64-apple-macos10.8 -isysroot macsdk-intel -o build/liboc2rnet-x86_64.dylib
-$CLANG $CFLAGS -Ijni-headers -fuse-ld=lld oc2rnet.c -shared -target arm64-apple-macos11.0 -isysroot macsdk-arm64 -o build/liboc2rnet-arm64.dylib
+$CLANG $CFLAGS -std=c99 -Ijni-headers -fuse-ld=lld oc2rnet.c -shared -target x86_64-apple-macos10.8 -isysroot macsdk-intel -o build/liboc2rnet-x86_64.dylib
+$CLANG $CFLAGS -std=c99 -Ijni-headers -fuse-ld=lld oc2rnet.c -shared -target arm64-apple-macos11.0 -isysroot macsdk-arm64 -o build/liboc2rnet-arm64.dylib
 
 # build for other platforms
 
@@ -37,10 +37,10 @@ if ! [ -d zig ]; then
     mv zig-* zig
 fi
 
-zig/zig cc $CFLAGS -Ijni-headers oc2rnet.c -shared -target x86_64-linux-gnu -o build/liboc2rnet-linux-x86_64.so
-zig/zig cc $CFLAGS -Ijni-headers oc2rnet.c -shared -target aarch64-linux-gnu -o build/liboc2rnet-linux-arm64.so
-zig/zig cc $CFLAGS -Ijni-headers oc2rnet.c -shared -target x86_64-windows-gnu -o build/oc2rnet-x86_64.dll -licmp
-zig/zig cc $CFLAGS -Ijni-headers oc2rnet.c -shared -target aarch64-windows-gnu -o build/oc2rnet-arm64.dll -licmp
+zig/zig cc $CFLAGS -std=c99 -D_DEFAULT_SOURCE -Ijni-headers oc2rnet.c -shared -target x86_64-linux-gnu -o build/liboc2rnet-linux-x86_64.so
+zig/zig cc $CFLAGS -std=c99 -D_DEFAULT_SOURCE -Ijni-headers oc2rnet.c -shared -target aarch64-linux-gnu -o build/liboc2rnet-linux-arm64.so
+zig/zig cc $CFLAGS -std=c99 -Ijni-headers oc2rnet.c -shared -target x86_64-windows-gnu -o build/oc2rnet-x86_64.dll -licmp
+zig/zig cc $CFLAGS -std=c99 -Ijni-headers oc2rnet.c -shared -target aarch64-windows-gnu -o build/oc2rnet-arm64.dll -licmp
 
 rm build/*.lib