diff --git a/extras/CustomTarget_templates.mk b/extras/CustomTarget_templates.mk
index 9754985f1a59..a0661e96b356 100644
--- a/extras/CustomTarget_templates.mk
+++ b/extras/CustomTarget_templates.mk
@@ -17,7 +17,7 @@ $(call gb_Trace_StartRange,$(subst $(gb_CustomTarget_workdir)/extras/source/,,$@
 cd $(dir $<) && \
 $(call gb_Helper_wsl_path,\
 $(WSL) zip -q0X --filesync --must-match $@ mimetype && \
-$(WSL) zip -qrX --must-match $@ $(subst $(dir $<),,$^))
+$(WSL) zip -qrX --must-match $@ $(subst $(dir $<),,$^)) -x mimetype
 $(call gb_Trace_EndRange,$(subst $(gb_CustomTarget_workdir)/extras/source/,,$@),ZIP)
 endef