diff --git a/RELEASES.md b/RELEASES.md
index c9b8cd7e..00c8e518 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -39,8 +39,11 @@ Build System
   accommodate liza-proguic's step-level package generation.
 - Step-level program packages are now properly accounted for as dependencies
   for builds.
-- `supplier.mk` generation will no longer be verbose (it'll instead be only
-  one line), which makes it more amenable to more frequent regeneration.
+- `supplier.mk` is now automatically regenerated when source files
+  change.  This previously needed to be done manually when imports changed.
+  - `supplier.mk` generation will no longer be verbose (it'll instead be
+    only one line), which makes it more amenable to more frequent
+    regeneration.
 
 
 v17.7.0 (2020-12-09)
diff --git a/build-aux/Makefile.am b/build-aux/Makefile.am
index bcdaa46a..76b96e99 100644
--- a/build-aux/Makefile.am
+++ b/build-aux/Makefile.am
@@ -82,6 +82,13 @@ package_dfns_pkgs = $(shell \
 )
 package_dfns_xmlos = $(patsubst %.xml, %.xmlo, $(package_dfns_pkgs))
 
+# Dependencies for suppliers.mk.
+src_suppliersmk = $(src_common) \
+                  $(shell find $(path_suppliers) ui/package ui/map rater/core -name '*.xml') \
+                  $(program_fragments) \
+                  ui/program.xml \
+                  ui/package-dfns.xml
+
 compiled_suppliers := $(src_suppliers:.xml=.xmlo)
 linked_suppliers   := $(src_suppliers:.xml=.xmle)
 
@@ -258,11 +265,12 @@ clean:
 		| sed 's/\.csvm$$/\.xml/; s/\.dat$$/\.xml/' \
 		| xargs rm -fv
 
-# generates a Makefile that will properly build all package dependencies; note
-# that territory and rate packages also have includes; see top of this file for
-# an explanation
-suppliers.mk: $(path_ui)/package-dfns.xml
-	$(ant) -q pkg-dep
+# Generates a Makefile that will properly build all package
+# dependencies.  The redirect of ant to /dev/null is because it's still too
+# noisy even with -q---the "BUILD SUCCESSFUL" line is confusing, considering
+# it's merely a small part of a broader build.
+suppliers.mk: $(src_suppliersmk)
+	$(ant) -q pkg-dep >/dev/null
 	find $(path_ui)/program/ -name '*.dep' | xargs cat $(path_ui)/program.dep | sort -u \
 	  > $(path_ui)/package-dfns.dep
 	$(RM) $(path_ui)/program.dep