diff --git a/Makefile.pre.in b/Makefile.pre.in
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -526,6 +526,12 @@
 	: # build lcov report
 	$(MAKE) coverage-lcov
 
+# Run "Argument Clinic" over all source files
+# (depends on python having already been built)
+.PHONY=clinic
+clinic: $(BUILDPYTHON)
+	$(RUNSHARED) $(PYTHON_FOR_BUILD) ./Tools/clinic/clinic.py */*.c
+
 # Build the interpreter
 $(BUILDPYTHON):	Modules/python.o $(LIBRARY) $(LDLIBRARY) $(PY3LIBRARY)
 	$(LINKCC) $(PY_LDFLAGS) $(LINKFORSHARED) -o $@ Modules/python.o $(BLDLIBRARY) $(LIBS) $(MODLIBS) $(SYSLIBS) $(LDLAST)
diff --git a/Tools/clinic/clinic.py b/Tools/clinic/clinic.py
--- a/Tools/clinic/clinic.py
+++ b/Tools/clinic/clinic.py
@@ -957,7 +957,6 @@
         dsl_name = block.dsl_name
         write = self.f.write
 
-        assert (not input) or (input.endswith('\n'))
         assert not ((dsl_name == None) ^ (output == None)), "you must specify dsl_name and output together, dsl_name " + repr(dsl_name)
 
         if not dsl_name:
@@ -1091,7 +1090,11 @@
     clinic = Clinic(language, verify=verify, filename=filename)
 
     with open(filename, 'r', encoding=encoding) as f:
-        text = clinic.parse(f.read())
+        raw = f.read()
+
+    cooked = clinic.parse(raw)
+    if cooked == raw:
+        return
 
     directory = os.path.dirname(filename) or '.'