diff --git a/ports/cc3200/application.mk b/ports/cc3200/application.mk
index deee201eef..7a8fb8d943 100644
--- a/ports/cc3200/application.mk
+++ b/ports/cc3200/application.mk
@@ -241,6 +241,3 @@ $(OBJ): | $(GEN_PINS_HDR)
 $(GEN_PINS_SRC) $(GEN_PINS_HDR) $(GEN_PINS_QSTR): $(BOARD_PINS) $(MAKE_PINS) $(AF_FILE) $(PREFIX_FILE) | $(HEADER_BUILD)
 	$(ECHO) "Create $@"
 	$(Q)$(PYTHON) $(MAKE_PINS) --board $(BOARD_PINS) --af $(AF_FILE) --prefix $(PREFIX_FILE) --hdr $(GEN_PINS_HDR) --qstr $(GEN_PINS_QSTR) > $(GEN_PINS_SRC)
-
-$(BUILD)/pins.o: $(BUILD)/pins.c
-	$(call compile_c)
diff --git a/ports/mimxrt/Makefile b/ports/mimxrt/Makefile
index 6131a509d8..c22c5442a9 100644
--- a/ports/mimxrt/Makefile
+++ b/ports/mimxrt/Makefile
@@ -510,7 +510,4 @@ $(BUILD)/%_gen.c $(HEADER_BUILD)/%.h: $(BOARD_PINS) $(MAKE_PINS) $(AF_FILE) $(PR
 		--iomux $(abspath $(TOP)/$(MCU_DIR)/drivers/fsl_iomuxc.h) \
 		--prefix $(PREFIX_FILE) --hdr $(GEN_PINS_HDR) > $(GEN_PINS_SRC)
 
-$(GEN_PINS_SRC:.c=.o): $(GEN_PINS_SRC)
-	$(call compile_c)
-
 include $(TOP)/py/mkrules.mk
diff --git a/ports/nrf/Makefile b/ports/nrf/Makefile
index ac86ad2b15..abc1ed497d 100644
--- a/ports/nrf/Makefile
+++ b/ports/nrf/Makefile
@@ -547,9 +547,6 @@ $(BUILD)/%_gen.c $(HEADER_BUILD)/%.h $(HEADER_BUILD)/%_af_const.h $(BUILD)/%_qst
 	$(ECHO) "Create $@"
 	$(Q)$(PYTHON) $(MAKE_PINS) --board $(BOARD_PINS) --af $(AF_FILE) --prefix $(PREFIX_FILE) --hdr $(GEN_PINS_HDR) --qstr $(GEN_PINS_QSTR) --af-const $(GEN_PINS_AF_CONST) --af-py $(GEN_PINS_AF_PY) > $(GEN_PINS_SRC)
 
-$(GEN_PINS_SRC:.c=.o): $(GEN_PINS_SRC)
-	$(call compile_c)
-
 $(PY_BUILD)/nlr%.o: CFLAGS += -Os -fno-lto
 
 include ../../py/mkrules.mk
diff --git a/ports/renesas-ra/Makefile b/ports/renesas-ra/Makefile
index fb7bb67e48..943ed6d9bf 100644
--- a/ports/renesas-ra/Makefile
+++ b/ports/renesas-ra/Makefile
@@ -586,9 +586,6 @@ $(BUILD)/%_$(BOARD).c $(HEADER_BUILD)/%.h $(HEADER_BUILD)/%_af_const.h $(HEADER_
 	$(ECHO) "GEN $@"
 	$(Q)$(PYTHON) $(MAKE_PINS) --board $(BOARD_PINS) --af $(AF_FILE) --prefix $(PREFIX_FILE) --hdr $(GEN_PINS_HDR) --qstr $(GEN_PINS_QSTR) --ad-const $(GEN_PINS_AD_CONST) --af-const $(GEN_PINS_AF_CONST) --af-py $(GEN_PINS_AF_PY) > $(GEN_PINS_SRC)
 
-#$(BUILD)/pins_$(BOARD).o: $(BUILD)/pins_$(BOARD).c
-#	$(call compile_c)
-
 CMSIS_MCU_HDR = $(CMSIS_DIR)/$(CMSIS_MCU_LOWER).h
 
 include $(TOP)/py/mkrules.mk
diff --git a/ports/stm32/Makefile b/ports/stm32/Makefile
index d3b80ab5b1..8d920ae953 100644
--- a/ports/stm32/Makefile
+++ b/ports/stm32/Makefile
@@ -684,9 +684,6 @@ $(BUILD)/%_$(BOARD).c $(HEADER_BUILD)/%.h $(HEADER_BUILD)/%_af_const.h $(HEADER_
 		--af-defs $(GEN_PINS_AF_DEFS) --af-defs-cmp-strings \
 		--af-py $(GEN_PINS_AF_PY) > $(GEN_PINS_SRC)
 
-$(GEN_PINS_SRC:.c=.o): $(GEN_PINS_SRC)
-	$(call compile_c)
-
 modmachine.c: $(GEN_PLLFREQTABLE_HDR)
 $(GEN_PLLFREQTABLE_HDR): $(PLLVALUES) | $(HEADER_BUILD)
 	$(ECHO) "GEN $@"
diff --git a/py/mkrules.mk b/py/mkrules.mk
index 8b21c7974d..5076559328 100644
--- a/py/mkrules.mk
+++ b/py/mkrules.mk
@@ -97,6 +97,10 @@ $(BUILD)/%.pp: %.c
 	$(ECHO) "PreProcess $<"
 	$(Q)$(CPP) $(CFLAGS) -Wp,-C,-dD,-dI -o $@ $<
 
+# Special case for compiling auto-generated source files.
+$(BUILD)/%.o: $(BUILD)/%.c
+	$(call compile_c)
+
 # The following rule uses | to create an order only prerequisite. Order only
 # prerequisites only get built if they don't exist. They don't cause timestamp
 # checking to be performed.
diff --git a/shared/memzip/README.md b/shared/memzip/README.md
index 3938e3198c..6ffe1d2c6f 100644
--- a/shared/memzip/README.md
+++ b/shared/memzip/README.md
@@ -18,9 +18,6 @@ OBJ += $(BUILD)/memzip-files.o
 
 MAKE_MEMZIP = ../shared/memzip/make-memzip.py
 
-$(BUILD)/memzip-files.o: $(BUILD)/memzip-files.c
-    $(call compile_c)
-
 $(BUILD)/memzip-files.c: $(shell find ${MEMZIP_DIR} -type f)
     @$(ECHO) "Creating $@"
     $(Q)$(PYTHON) $(MAKE_MEMZIP) --zip-file $(BUILD)/memzip-files.zip --c-file $@ $(MEMZIP_DIR)