diff --git a/Makefile b/Makefile
index 87e62adb5..e5ca83aea 100644
--- a/Makefile
+++ b/Makefile
@@ -993,6 +993,9 @@ docs/source/cell/word_add.rst: $(TARGETS) $(EXTRA_TARGETS)
 	$(Q) rsync -rc temp/docs/source/cell docs/source
 	$(Q) rm -rf temp
 
+docs/source/generated/cells.json: docs/source/generated $(TARGETS) $(EXTRA_TARGETS)
+	$(Q) ./$(PROGRAM_PREFIX)yosys -p 'help -dump-cells-json $@'
+
 PHONY: docs/gen_examples docs/gen_images docs/guidelines docs/usage docs/reqs
 docs/gen_examples: $(TARGETS)
 	$(Q) $(MAKE) -C docs examples
@@ -1034,7 +1037,7 @@ docs/reqs:
 	$(Q) $(MAKE) -C docs reqs
 
 .PHONY: docs/prep
-docs/prep: docs/source/cmd/abc.rst docs/source/cell/word_add.rst docs/gen_examples docs/gen_images docs/guidelines docs/usage
+docs/prep: docs/source/cmd/abc.rst docs/source/generated/cells.json docs/gen_examples docs/gen_images docs/guidelines docs/usage
 
 DOC_TARGET ?= html
 docs: docs/prep