diff --git a/src/dotty/tools/dotc/typer/ProtoTypes.scala b/src/dotty/tools/dotc/typer/ProtoTypes.scala
index 0e6697fb730a..751ed928bf8e 100644
--- a/src/dotty/tools/dotc/typer/ProtoTypes.scala
+++ b/src/dotty/tools/dotc/typer/ProtoTypes.scala
@@ -395,9 +395,10 @@ object ProtoTypes {
           if (mt.isDependent) tp
           else {
             val rt = normalize(mt.resultType, pt)
-            if (pt.isInstanceOf[ApplyingProto])
-              mt.derivedMethodType(mt.paramNames, mt.paramTypes, rt)
-            else {
+          pt match {
+            case pt: IgnoredProto  => mt
+            case pt: ApplyingProto => mt.derivedMethodType(mt.paramNames, mt.paramTypes, rt)
+            case _ =>
               val ft = defn.FunctionOf(mt.paramTypes, rt)
               if (mt.paramTypes.nonEmpty || ft <:< pt) ft else rt
             }
diff --git a/tests/run/i1543.check b/tests/run/i1543.check
new file mode 100644
index 000000000000..10adcaf83eb4
--- /dev/null
+++ b/tests/run/i1543.check
@@ -0,0 +1,31 @@
+1
+2
+3
+4
+5
+6
+7
+8
+9
+10
+11
+12
+13
+14
+15
+16
+17
+18
+19
+20
+21
+22
+23
+24
+25
+26
+27
+28
+29
+30
+31
diff --git a/tests/run/i1543.scala b/tests/run/i1543.scala
new file mode 100644
index 000000000000..268bc717bb59
--- /dev/null
+++ b/tests/run/i1543.scala
@@ -0,0 +1,41 @@
+
+object Test extends dotty.runtime.LegacyApp {
+  new Bar().foo(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
+}
+
+
+class Bar {
+  def foo(p1: Int, p2: Int, p3: Int, p4: Int, p5: Int, p6: Int, p7: Int, p8: Int, p9: Int, p10: Int, p11: Int, p12: Int, p13: Int, p14: Int, p15: Int, p16: Int, p17: Int, p18: Int, p19: Int, p20: Int, p21: Int, p22: Int, p23: Int, p24: Int, p25: Int, p26: Int, p27: Int, p28: Int, p29: Int, p30: Int, p31: Int): Unit = {
+    println(p1)
+    println(p2)
+    println(p3)
+    println(p4)
+    println(p5)
+    println(p6)
+    println(p7)
+    println(p8)
+    println(p9)
+    println(p10)
+    println(p11)
+    println(p12)
+    println(p13)
+    println(p14)
+    println(p15)
+    println(p16)
+    println(p17)
+    println(p18)
+    println(p19)
+    println(p20)
+    println(p21)
+    println(p22)
+    println(p23)
+    println(p24)
+    println(p25)
+    println(p26)
+    println(p27)
+    println(p28)
+    println(p29)
+    println(p30)
+    println(p31)
+  }
+}