diff --git a/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp b/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
--- a/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
+++ b/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
@@ -520,8 +520,14 @@
   for (const BasicBlock &BB : F) {
     // If we have any returns of `musttail` results - the signature can't
     // change
-    if (BB.getTerminatingMustTailCall() != nullptr)
+    if (const auto *TC = BB.getTerminatingMustTailCall()) {
       HasMustTailCalls = true;
+      // In addition, if the called function is virtual, we can't change
+      // the return type.
+      if (!TC->getCalledFunction())
+        for (unsigned Ri = 0; Ri < RetCount; ++Ri)
+          RetValLiveness[Ri] = Live;
+    }
   }
 
   if (HasMustTailCalls) {
diff --git a/llvm/test/Transforms/DeadArgElim/musttail-indirect.ll b/llvm/test/Transforms/DeadArgElim/musttail-indirect.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Transforms/DeadArgElim/musttail-indirect.ll
@@ -0,0 +1,9 @@
+; RUN: opt -passes=deadargelim,verify -S < %s 2>&1 | FileCheck %s
+define internal i32 @test(ptr %fptr, i32 %a, i32 %b) {
+  %r = musttail call i32 %fptr(ptr %fptr, i32 %a, i32 0)
+  ret i32 %r
+}
+
+; CHECK-NOT: cannot guarantee tail call due to mismatched parameter counts
+; CHECK: define internal i32 @test
+; CHECK-NEXT: %r = musttail call i32 %fptr