diff --git a/tools/swift-serialize-diagnostics/swift-serialize-diagnostics.cpp b/tools/swift-serialize-diagnostics/swift-serialize-diagnostics.cpp
index 03b0118f2ee..8a65db5bf19 100644
--- a/tools/swift-serialize-diagnostics/swift-serialize-diagnostics.cpp
+++ b/tools/swift-serialize-diagnostics/swift-serialize-diagnostics.cpp
@@ -86,7 +86,7 @@ int main(int argc, char *argv[]) {
   // Print out the diagnostics IDs that are available in YAML but not available
   // in `.def`
   if (!yaml.unknownIDs.empty()) {
-    llvm::errs() << "These diagnostic IDs are no longer availiable: '";
+    llvm::errs() << "These diagnostic IDs are no longer available: '";
     llvm::interleave(
         yaml.unknownIDs, [&](std::string id) { llvm::errs() << id; },
         [&] { llvm::errs() << ", "; });