diff --git a/mflag/flag.go b/mflag/flag.go
index 2ad299a..e7fabe0 100644
--- a/mflag/flag.go
+++ b/mflag/flag.go
@@ -1223,11 +1223,27 @@ func (v mergeVal) IsBoolFlag() bool {
 	return false
 }
 
+// Name returns the name of a mergeVal.
+// If the original value had a name, return the original name,
+// otherwise, return the key asinged to this mergeVal.
+func (v mergeVal) Name() string {
+	type namedValue interface {
+		Name() string
+	}
+	if nVal, ok := v.Value.(namedValue); ok {
+		return nVal.Name()
+	}
+	return v.key
+}
+
 // Merge is an helper function that merges n FlagSets into a single dest FlagSet
 // In case of name collision between the flagsets it will apply
 // the destination FlagSet's errorHandling behavior.
 func Merge(dest *FlagSet, flagsets ...*FlagSet) error {
 	for _, fset := range flagsets {
+		if fset.formal == nil {
+			continue
+		}
 		for k, f := range fset.formal {
 			if _, ok := dest.formal[k]; ok {
 				var err error
@@ -1249,6 +1265,9 @@ func Merge(dest *FlagSet, flagsets ...*FlagSet) error {
 			}
 			newF := *f
 			newF.Value = mergeVal{f.Value, k, fset}
+			if dest.formal == nil {
+				dest.formal = make(map[string]*Flag)
+			}
 			dest.formal[k] = &newF
 		}
 	}
diff --git a/mflag/flag_test.go b/mflag/flag_test.go
index c28deda..1383555 100644
--- a/mflag/flag_test.go
+++ b/mflag/flag_test.go
@@ -514,3 +514,14 @@ func TestSortFlags(t *testing.T) {
 		t.Fatalf("NFlag (%d) != fs.NFlag() (%d) of elements visited", nflag, fs.NFlag())
 	}
 }
+
+func TestMergeFlags(t *testing.T) {
+	base := NewFlagSet("base", ContinueOnError)
+	base.String([]string{"f"}, "", "")
+
+	fs := NewFlagSet("test", ContinueOnError)
+	Merge(fs, base)
+	if len(fs.formal) != 1 {
+		t.Fatalf("FlagCount (%d) != number (1) of elements merged", len(fs.formal))
+	}
+}