diff --git a/stdlib/public/Platform/Platform.swift b/stdlib/public/Platform/Platform.swift
index 0c2d63a0cffdb..ca7417c53574b 100644
--- a/stdlib/public/Platform/Platform.swift
+++ b/stdlib/public/Platform/Platform.swift
@@ -84,6 +84,11 @@ func _convertDarwinBooleanToBool(_ x: DarwinBoolean) -> Bool {
 
 #endif
 
+// wasi-libc defines `errno` in a way ClangImporter can understand, so we don't
+// need to define shims for it. On the contrary, if we define the shim, we will
+// get an ambiguity error when importing WASILibc module and SwiftWASILibc Clang
+// module (or a Clang module that re-exports SwiftWASILibc).
+#if !os(WASI)
 //===----------------------------------------------------------------------===//
 // sys/errno.h
 //===----------------------------------------------------------------------===//
@@ -96,6 +101,7 @@ public var errno : Int32 {
     return _swift_stdlib_setErrno(val)
   }
 }
+#endif
 
 
 //===----------------------------------------------------------------------===//
diff --git a/stdlib/public/Platform/WASILibc.swift.gyb b/stdlib/public/Platform/WASILibc.swift.gyb
index f3d5f2486701a..9331e3f6a8420 100644
--- a/stdlib/public/Platform/WASILibc.swift.gyb
+++ b/stdlib/public/Platform/WASILibc.swift.gyb
@@ -73,6 +73,7 @@ posix_error_codes = [
   "EADDRNOTAVAIL",
   "EAFNOSUPPORT",
   "EAGAIN",
+  "EWOULDBLOCK",
   "EALREADY",
   "EBADF",
   "EBADMSG",
@@ -125,6 +126,7 @@ posix_error_codes = [
   "ENOTRECOVERABLE",
   "ENOTSOCK",
   "ENOTSUP",
+  "EOPNOTSUPP",
   "ENOTTY",
   "ENXIO",
   "EOVERFLOW",