diff --git a/pkg/obingslibrary/multimatch.go b/pkg/obingslibrary/multimatch.go
index b28befa..3d32942 100644
--- a/pkg/obingslibrary/multimatch.go
+++ b/pkg/obingslibrary/multimatch.go
@@ -777,7 +777,7 @@ func (library *NGSLibrary) ExtractMultiBarcodeSliceWorker(options ...WithOption)
 		library.SetAllowsIndels(true)
 	}
 
-	if opt.AllowedMismatches() > 0 {
+	if opt.AllowedMismatchesIsSet() {
 		library.SetAllowedMismatches(opt.AllowedMismatches())
 	}
 
diff --git a/pkg/obingslibrary/worker.go b/pkg/obingslibrary/worker.go
index 2cfe391..75347f6 100644
--- a/pkg/obingslibrary/worker.go
+++ b/pkg/obingslibrary/worker.go
@@ -6,13 +6,14 @@ import (
 )
 
 type _Options struct {
-	discardErrors   bool
-	unidentified    string
-	allowedMismatch int
-	allowsIndel     bool
-	withProgressBar bool
-	parallelWorkers int
-	batchSize       int
+	discardErrors      bool
+	unidentified       string
+	allowedMismatch    int
+	allowedMismatchSet bool
+	allowsIndel        bool
+	withProgressBar    bool
+	parallelWorkers    int
+	batchSize          int
 }
 
 // Options stores a set of option usable by the
@@ -52,6 +53,7 @@ func OptionWithProgressBar(yes bool) WithOption {
 func OptionAllowedMismatches(count int) WithOption {
 	f := WithOption(func(opt Options) {
 		opt.pointer.allowedMismatch = count
+		opt.pointer.allowedMismatchSet = true
 	})
 
 	return f
@@ -97,6 +99,12 @@ func (options Options) AllowedMismatches() int {
 	return options.pointer.allowedMismatch
 }
 
+// AllowedMismatchesIsSet returns true if OptionAllowedMismatches
+// was explicitly applied to these options.
+func (options Options) AllowedMismatchesIsSet() bool {
+	return options.pointer.allowedMismatchSet
+}
+
 func (options Options) AllowsIndels() bool {
 	return options.pointer.allowsIndel
 }
diff --git a/pkg/obitools/obimultiplex/demultiplex.go b/pkg/obitools/obimultiplex/demultiplex.go
index 064e4d5..996843b 100644
--- a/pkg/obitools/obimultiplex/demultiplex.go
+++ b/pkg/obitools/obimultiplex/demultiplex.go
@@ -15,7 +15,6 @@ func IExtractBarcode(iterator obiiter.IBioSequence) (obiiter.IBioSequence, error
 	opts := make([]obingslibrary.WithOption, 0, 10)
 
 	opts = append(opts,
-		obingslibrary.OptionAllowedMismatches(CLIAllowedMismatch()),
 		obingslibrary.OptionAllowedIndel(CLIAllowsIndel()),
 		obingslibrary.OptionUnidentified(CLIUnidentifiedFileName()),
 		obingslibrary.OptionDiscardErrors(!CLIConservedErrors()),
@@ -23,6 +22,14 @@ func IExtractBarcode(iterator obiiter.IBioSequence) (obiiter.IBioSequence, error
 		obingslibrary.OptionBatchSize(obidefault.BatchSize()),
 	)
 
+	// Only propagate the CLI --allowed-mismatches value if the user
+	// explicitly set it: otherwise the per-primer values defined in
+	// the NGSFilter config file (@primer_mismatches, @forward_mismatches,
+	// @reverse_mismatches) must be preserved.
+	if CLIAllowedMismatchIsSet() {
+		opts = append(opts, obingslibrary.OptionAllowedMismatches(CLIAllowedMismatch()))
+	}
+
 	ngsfilter, err := CLINGSFIlter()
 	if err != nil {
 		log.Fatalf("%v", err)
diff --git a/pkg/obitools/obimultiplex/options.go b/pkg/obitools/obimultiplex/options.go
index 3809d76..7fd4897 100644
--- a/pkg/obitools/obimultiplex/options.go
+++ b/pkg/obitools/obimultiplex/options.go
@@ -18,6 +18,7 @@ var _UnidentifiedFile = ""
 var _AllowedMismatch = 2
 var _AllowsIndel = false
 var _ConservedError = false
+var _optionsParser *getoptions.GetOpt
 
 // PCROptionSet defines every options related to a simulated PCR.
 //
@@ -29,6 +30,8 @@ var _ConservedError = false
 // - option : is a pointer to a getoptions.GetOpt instance normaly
 // produced by the
 func MultiplexOptionSet(options *getoptions.GetOpt) {
+	_optionsParser = options
+
 	options.StringVar(&_NGSFilterFile, "tag-list", _NGSFilterFile,
 		options.Alias("s"),
 		options.Description("File name of the NGSFilter file describing PCRs."))
@@ -62,6 +65,15 @@ func CLIAllowedMismatch() int {
 	return _AllowedMismatch
 }
 
+// CLIAllowedMismatchIsSet returns true if the user explicitly
+// specified --allowed-mismatches on the command line, as opposed
+// to relying on its default value. This allows per-primer mismatch
+// settings from the NGSFilter config file to take precedence unless
+// the user explicitly overrides them from the CLI.
+func CLIAllowedMismatchIsSet() bool {
+	return _optionsParser != nil && _optionsParser.Called("allowed-mismatches")
+}
+
 func CLIAllowsIndel() bool {
 	return _AllowsIndel
 }
diff --git a/pkg/obitools/obitagpcr/pcrtag.go b/pkg/obitools/obitagpcr/pcrtag.go
index bd32402..a6c7f31 100644
--- a/pkg/obitools/obitagpcr/pcrtag.go
+++ b/pkg/obitools/obitagpcr/pcrtag.go
@@ -55,7 +55,7 @@ func IPCRTagPESequencesBatch(iterator obiiter.IBioSequence,
 		ngsfilter.SetAllowsIndels(true)
 	}
 
-	if obimultiplex.CLIAllowedMismatch() > 0 {
+	if obimultiplex.CLIAllowedMismatchIsSet() {
 		ngsfilter.SetAllowedMismatches(obimultiplex.CLIAllowedMismatch())
 	}