diff --git a/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp b/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
index 4883d83647d..a8b93ca8a2f 100644
--- a/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
+++ b/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
@@ -313,14 +313,16 @@ WebAssemblyTargetLowering::LowerCall(CallLoweringInfo &CLI,
 
   SmallVectorImpl<ISD::OutputArg> &Outs = CLI.Outs;
   for (const ISD::OutputArg &Out : Outs) {
-    assert(!Out.Flags.isByVal() && "byval is not valid for return values");
-    assert(!Out.Flags.isNest() && "nest is not valid for return values");
+    if (Out.Flags.isByVal())
+      fail(DL, DAG, "WebAssembly hasn't implemented byval arguments");
+    if (Out.Flags.isNest())
+      fail(DL, DAG, "WebAssembly hasn't implemented nest arguments");
     if (Out.Flags.isInAlloca())
-      fail(DL, DAG, "WebAssembly hasn't implemented inalloca results");
+      fail(DL, DAG, "WebAssembly hasn't implemented inalloca arguments");
     if (Out.Flags.isInConsecutiveRegs())
-      fail(DL, DAG, "WebAssembly hasn't implemented cons regs results");
+      fail(DL, DAG, "WebAssembly hasn't implemented cons regs arguments");
     if (Out.Flags.isInConsecutiveRegsLast())
-      fail(DL, DAG, "WebAssembly hasn't implemented cons regs last results");
+      fail(DL, DAG, "WebAssembly hasn't implemented cons regs last arguments");
   }
 
   bool IsVarArg = CLI.IsVarArg;
@@ -388,16 +390,14 @@ WebAssemblyTargetLowering::LowerCall(CallLoweringInfo &CLI,
 
   SmallVector<EVT, 8> Tys;
   for (const auto &In : Ins) {
-    if (In.Flags.isByVal())
-      fail(DL, DAG, "WebAssembly hasn't implemented byval arguments");
+    assert(!In.Flags.isByVal() && "byval is not valid for return values");
+    assert(!In.Flags.isNest() && "nest is not valid for return values");
     if (In.Flags.isInAlloca())
-      fail(DL, DAG, "WebAssembly hasn't implemented inalloca arguments");
-    if (In.Flags.isNest())
-      fail(DL, DAG, "WebAssembly hasn't implemented nest arguments");
+      fail(DL, DAG, "WebAssembly hasn't implemented inalloca return values");
     if (In.Flags.isInConsecutiveRegs())
-      fail(DL, DAG, "WebAssembly hasn't implemented cons regs arguments");
+      fail(DL, DAG, "WebAssembly hasn't implemented cons regs return values");
     if (In.Flags.isInConsecutiveRegsLast())
-      fail(DL, DAG, "WebAssembly hasn't implemented cons regs last arguments");
+      fail(DL, DAG, "WebAssembly hasn't implemented cons regs last return values");
     // Ignore In.getOrigAlign() because all our arguments are passed in
     // registers.
     Tys.push_back(In.VT);