diff --git a/_test/assign13.go b/_test/assign13.go
new file mode 100644
index 00000000..62bde505
--- /dev/null
+++ b/_test/assign13.go
@@ -0,0 +1,19 @@
+package main
+
+import "fmt"
+
+func getStr() string {
+	return "test"
+}
+
+func main() {
+	m := make(map[string]string, 0)
+	m["a"] = fmt.Sprintf("%v", 0.1)
+	m["b"] = string(fmt.Sprintf("%v", 0.1))
+	m["c"] = getStr()
+
+	fmt.Println(m)
+}
+
+// Output:
+// map[a:0.1 b:0.1 c:test]
diff --git a/interp/cfg.go b/interp/cfg.go
index a3346321..e39be2e9 100644
--- a/interp/cfg.go
+++ b/interp/cfg.go
@@ -521,7 +521,7 @@ func (interp *Interpreter) cfg(root *node, pkgID string) ([]*node, error) {
 				// Propagate type
 				// TODO: Check that existing destination type matches source type
 				switch {
-				case n.action == aAssign && isCall(src) && dest.typ.cat != interfaceT && !isRecursiveField(dest):
+				case n.action == aAssign && isCall(src) && dest.typ.cat != interfaceT && !isMapEntry(dest) && !isRecursiveField(dest):
 					// Call action may perform the assignment directly.
 					n.gen = nop
 					src.level = level
diff --git a/interp/run.go b/interp/run.go
index 99afa401..9f41c47d 100644
--- a/interp/run.go
+++ b/interp/run.go
@@ -1121,9 +1121,11 @@ func callBin(n *node) {
 		}
 	default:
 		switch n.anc.action {
-		case aAssign, aAssignX:
+		case aAssignX:
 			// The function call is part of an assign expression, store results direcly
 			// to assigned location, to avoid an additional frame copy.
+			// The optimization of aAssign is handled in assign(), and should not
+			// be handled here.
 			rvalues := make([]func(*frame) reflect.Value, funcType.NumOut())
 			for i := range rvalues {
 				c := n.anc.child[i]
@@ -1166,7 +1168,9 @@ func callBin(n *node) {
 					in[i] = v(f)
 				}
 				out := callFn(value(f), in)
-				copy(f.data[n.findex:], out)
+				for i := 0; i < len(out); i++ {
+					f.data[n.findex+i].Set(out[i])
+				}
 				return tnext
 			}
 		}