ifchange.go | 11 +++++++++++

diff --git a/ifchange.go b/ifchange.go
index eb5f57929c6c66680938a508a672c406c5449f15ecf050e6f6962d87a25cb720..1ee2e5898be688ca4fd62e1e8ff46a17eb28c9d78b21ed7fc9e7559f2d616886 100644
--- a/ifchange.go
+++ b/ifchange.go
@@ -179,6 +179,17 @@ 	goto RebuildDeps
 }
 
 func ifchange(tgts []string, forced, traced bool) (bool, error) {
+	// only unique elements
+	m := make(map[string]struct{})
+	for _, t := range tgts {
+		m[t] = struct{}{}
+	}
+	tgts = tgts[:0]
+	for t := range m {
+		tgts = append(tgts, t)
+	}
+	m = nil
+
 	jsInit()
 	if !IsTopRedo {
 		defer jsAcquire("ifchange exiting")