diff --git a/Configuration/Applications/python/ConfigBuilder.py b/Configuration/Applications/python/ConfigBuilder.py
index 334a5ced55fdb..ee88eae5b9749 100644
--- a/Configuration/Applications/python/ConfigBuilder.py
+++ b/Configuration/Applications/python/ConfigBuilder.py
@@ -16,6 +16,7 @@
 import collections
 from subprocess import Popen,PIPE
 import FWCore.ParameterSet.DictTypes as DictTypes
+from FWCore.ParameterSet.OrderedSet import OrderedSet
 class Options:
     pass
 
@@ -2052,7 +2053,7 @@ def prepare_DQM(self, stepSpec = 'DQMOffline'):
         self.expandMapping(postSequenceList,autoDQM,index=1)
 
         if len(set(sequenceList))!=len(sequenceList):
-            sequenceList=list(set(sequenceList))
+            sequenceList=list(OrderedSet(sequenceList))
             print("Duplicate entries for DQM:, using",sequenceList)
 
         pathName='dqmoffline_step'
@@ -2099,7 +2100,7 @@ def prepare_HARVESTING(self, stepSpec = None):
         self.expandMapping(harvestingList,combined_mapping,index=-1)
 
         if len(set(harvestingList))!=len(harvestingList):
-            harvestingList=list(set(harvestingList))
+            harvestingList=list(OrderedSet(harvestingList))
             print("Duplicate entries for HARVESTING, using",harvestingList)
 
         for name in harvestingList:
diff --git a/Configuration/Applications/test/BuildFile.xml b/Configuration/Applications/test/BuildFile.xml
new file mode 100644
index 0000000000000..81394fdef1c40
--- /dev/null
+++ b/Configuration/Applications/test/BuildFile.xml
@@ -0,0 +1 @@
+<test name="TestConfigurationApplicationsConfigBuilder" command="python3 ${LOCALTOP}/src/Configuration/Applications/test/ConfigBuilderTest.py"/>
diff --git a/Configuration/Applications/test/ConfigBuilderTest.py b/Configuration/Applications/test/ConfigBuilderTest.py
new file mode 100644
index 0000000000000..a01daa5558ce1
--- /dev/null
+++ b/Configuration/Applications/test/ConfigBuilderTest.py
@@ -0,0 +1,80 @@
+import FWCore.ParameterSet.Config as cms
+from Configuration.Applications.ConfigBuilder import ConfigBuilder, defaultOptions
+
+import copy
+
+def prepareDQMSequenceOrder():
+    options = copy.deepcopy(defaultOptions)
+    options.scenario = "Test"
+
+    process = cms.Process("Test")
+    process.a1 = cms.EDAnalyzer("A1")
+    process.a2 = cms.EDAnalyzer("A2")
+    process.a3 = cms.EDAnalyzer("A3")
+    process.a4 = cms.EDAnalyzer("A4")
+    process.seq1 = cms.Sequence(process.a1)
+    process.seq2 = cms.Sequence(process.a2)
+    process.seq3 = cms.Sequence(process.a3)
+    process.seq4 = cms.Sequence(process.a4)
+    process.ps1 = cms.Sequence()
+    process.ps2 = cms.Sequence()
+    process.ps3 = cms.Sequence()
+    process.ps3 = cms.Sequence()
+    process.ps4 = cms.Sequence()
+    return (options, process)
+
+if __name__=="__main__":
+    import unittest
+
+    class TestModuleCommand(unittest.TestCase):
+        def setUp(self):
+            """Nothing to do """
+            None
+
+        def testDQMSequenceOrder(self):
+            def extract(process, count):
+                if count == 0:
+                    return []
+                ret = list(process.dqmoffline_step.moduleNames())
+                for i in range(1, count):
+                    ret.extend(list(getattr(process, f"dqmoffline_{i}_step").moduleNames()))
+                return ret
+
+            # DQM sequences are unique
+            (options, process) = prepareDQMSequenceOrder()
+            order = [3, 1, 2]
+            cb = ConfigBuilder(options, process)
+            cb.prepare_DQM("+".join(f"seq{o}" for o in order))
+            self.assertEqual([f"a{o}" for o in order], extract(process, len(order)))
+
+            # Code in prepare_DQM() call assumes the 'sequenceList`
+            # has at least as many elements as `postSequenceList`. We
+            # can't fake 'postSequenceList' as it is also derived from
+            # the prepare_DQM() argument, but duplicates are not
+            # removed. The only handle we have (besides code changes,
+            # that are beyond this bug fix), is to modify the autoDQM.
+            from DQMOffline.Configuration.autoDQM import autoDQM
+            autoDQM_orig = copy.deepcopy(autoDQM)
+            autoDQM.clear()
+            autoDQM["alias1"] = ["seq1", "ps1", "not needed"]
+            autoDQM["alias2"] = ["seq2", "ps2", "not needed"]
+            autoDQM["alias3"] = ["seq3", "ps3", "not needed"]
+            # seq4 is used only to have the expanded and uniquified
+            # 'sequenceList' to have at least as many elements as
+            # 'postSequenceList'
+            autoDQM["alias4"] = ["seq2+seq4", "ps4", "not needed"]
+
+            order = [2, 1, 3]
+            cb = ConfigBuilder(options, process)
+            cb.prepare_DQM("+".join(f"@alias{o}" for o in order))
+            self.assertEqual([f"a{o}" for o in order], extract(process, len(order)))
+
+            cb = ConfigBuilder(options, process)
+            order = [2, 1, 4, 3]
+            cb.prepare_DQM("+".join(f"@alias{o}" for o in order))
+            self.assertEqual([f"a{o}" for o in order], extract(process, len(order)))
+
+            autoDQM.clear()
+            autoDQM.update(autoDQM_orig)
+
+    unittest.main()