diff --git a/require-ess/tools/driver.makefile b/require-ess/tools/driver.makefile
index f9a13412ae9753ff241fc39946b3302e9524ff1e..205886a800daa6c8038c6ac6272f13afec743726 100644
--- a/require-ess/tools/driver.makefile
+++ b/require-ess/tools/driver.makefile
@@ -868,7 +868,7 @@ ${DEPFILE}: ${LIBOBJS} $(USERMAKEFILE)
 	$(RM) $@.tmp
 	@echo "# Generated file. Do not edit." > $@
 # Check dependencies on other module headers.
-	cat *.d 2>/dev/null | sed 's/ /\n/g' | grep -v '$(EPICS_BASE)/include' | sed -n '$(DEP_PARSER)' >> $@.tmp
+	cat *.d 2>/dev/null | sed 's/ /\n/g' | grep -v '$(EPICS_BASE)/include' | sed -n '$(DEP_PARSER)' > $@.tmp
 # Manully added dependencies: ${REQ}
 	@$(foreach m,${REQ},echo "$m $(or $(and $(or $(wildcard $(EPICS_MODULES)/$m/$($m_VERSION)),$(wildcard $(E3_SITEMODS_PATH)/$m/$($m_VERSION))),$($m_VERSION)),$(error REQUIRED module '$m' version '$($m_VERSION)' does not exist))" >> $@.tmp;)
 	cat $@.tmp | sort -u >> $@