diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyFixBrTableDefaults.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyFixBrTableDefaults.cpp
--- a/llvm/lib/Target/WebAssembly/WebAssemblyFixBrTableDefaults.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyFixBrTableDefaults.cpp
@@ -52,24 +52,32 @@
 
   // Find the conditional jump to the default target. If it doesn't exist, the
   // default target is unreachable anyway, so we can choose anything.
-  auto JumpMII = --HeaderMBB->end();
-  while (JumpMII->getOpcode() != WebAssembly::BR_IF &&
-         JumpMII != HeaderMBB->begin()) {
-    --JumpMII;
-  }
-  if (JumpMII->getOpcode() == WebAssembly::BR_IF) {
-    // Install the default target and remove the jumps in the header.
-    auto *DefaultMBB = JumpMII->getOperand(0).getMBB();
-    assert(DefaultMBB != MBB && "Expected conditional jump to default target");
-    MI.addOperand(MF, MachineOperand::CreateMBB(DefaultMBB));
-    HeaderMBB->erase(JumpMII, HeaderMBB->end());
+  MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
+  SmallVector<MachineOperand, 2> Cond;
+  const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
+  TII.analyzeBranch(*HeaderMBB, TBB, FBB, Cond);
+
+  // Here are the possible outcomes. '_' is nullptr, `J` is the jump table block
+  // aka MBB, 'D' is the default block.
+  //
+  // TBB | FBB | Meaning
+  //  _  |  _  | No default block, header falls through to jump table
+  //  J  |  _  | No default block, header jumps to the jump table
+  //  D  |  _  | Header jumps to the default and falls through to the jump table
+  //  D  |  J  | Header jumps to the default and also to the jump table
+  if (TBB && TBB != MBB) {
+    // Install the default target.
+    assert((FBB == nullptr || FBB == MBB) &&
+           "Expected jump or fallthrough to br_table block");
+    MI.addOperand(MF, MachineOperand::CreateMBB(TBB));
   } else {
     // Arbitrarily choose the first jump target as the default.
     auto *SomeMBB = MI.getOperand(1).getMBB();
     MI.addOperand(MachineOperand::CreateMBB(SomeMBB));
   }
 
-  // Splice the jump table into the header.
+  // Remove any branches from the header and splice in the jump table instead
+  TII.removeBranch(*HeaderMBB, nullptr);
   HeaderMBB->splice(HeaderMBB->end(), MBB, MBB->begin(), MBB->end());
 
   // Update CFG to skip the old jump table block. Remove shared successors
diff --git a/llvm/test/CodeGen/WebAssembly/switch-unreachable-default.ll b/llvm/test/CodeGen/WebAssembly/switch-unreachable-default.ll
--- a/llvm/test/CodeGen/WebAssembly/switch-unreachable-default.ll
+++ b/llvm/test/CodeGen/WebAssembly/switch-unreachable-default.ll
@@ -36,3 +36,52 @@
 unreachable:
   unreachable
 }
+
+; CHECK-LABEL: split:
+; CHECK:    .functype split (i32) -> ()
+; CHECK:    block
+; CHECK:    br_if 0
+; CHECK:    block
+; CHECK:    block
+; CHECK:    br_table {1, 1, 1, 1, 1, 1, 1, 0}
+; CHECK: .LBB1_2
+; CHECK:    end_block
+; CHECK:    br_table {0, 0, 0}
+; CHECK: .LBB1_3
+; CHECK:    end_block
+; CHECK:    unreachable
+; CHECK: .LBB1_4
+; CHECK:    end_block
+; CHECK:    end_function
+define void @split(i8 %c) {
+entry:
+  switch i8 %c, label %sw.default [
+    i8 114, label %return
+    i8 103, label %sw.bb1
+    i8 98, label %sw.bb2
+    i8 97, label %sw.bb3
+    i8 48, label %sw.bb4
+    i8 49, label %sw.bb5
+  ]
+
+sw.bb1:
+  unreachable
+
+sw.bb2:
+  unreachable
+
+sw.bb3:
+  unreachable
+
+sw.bb4:
+  unreachable
+
+sw.bb5:
+  unreachable
+
+sw.default:
+  unreachable
+
+return:
+  ret void
+}