diff --git a/lib/Sema/CSGen.cpp b/lib/Sema/CSGen.cpp
index 6f8c9a43a78a5..deea7c496a818 100644
--- a/lib/Sema/CSGen.cpp
+++ b/lib/Sema/CSGen.cpp
@@ -3997,6 +3997,10 @@ namespace {
       auto results = namelookup::lookupMacros(CurDC, DeclNameRef(moduleName),
                                               DeclNameRef(macroName), roles);
       for (const auto &result : results) {
+        // Ignore invalid results. This matches the OverloadedDeclRefExpr
+        // logic.
+        if (result->isInvalid())
+          continue;
         OverloadChoice choice = OverloadChoice(Type(), result, functionRefKind);
         choices.push_back(choice);
       }
diff --git a/test/Constraints/issue-77393.swift b/test/Constraints/issue-77393.swift
new file mode 100644
index 0000000000000..e67e9a5bdb0b5
--- /dev/null
+++ b/test/Constraints/issue-77393.swift
@@ -0,0 +1,24 @@
+// RUN: %target-typecheck-verify-swift
+
+// https://github.com/swiftlang/swift/issues/77393
+// Make sure we don't crash.
+
+@freestanding(expression)
+macro someMacro() = #externalMacro(module: "", type: "")
+// expected-warning@-1 {{external macro implementation type '.' could not be found for macro 'someMacro()'; plugin for module '' not found}}
+// expected-note@-2 {{'someMacro()' previously declared here}}
+// expected-note@-3 {{'someMacro()' declared here}}
+
+@freestanding(expression)
+macro someMacro() = #externalMacro(module: "", type: "")
+// expected-error@-1 {{invalid redeclaration of 'someMacro()'}}
+// expected-warning@-2 {{external macro implementation type '.' could not be found for macro 'someMacro()'; plugin for module '' not found}}
+
+#someMacro()
+// expected-error@-1 {{external macro implementation type '.' could not be found for macro 'someMacro()'; plugin for module '' not found}}
+
+macro invalidMacro()
+// expected-error@-1 {{macro 'invalidMacro()' requires a definition}}
+// expected-error@-2 {{macro 'invalidMacro()' must declare its applicable roles via '@freestanding' or @attached'}}
+
+#invalidMacro() // expected-error {{no macro named 'invalidMacro'}}