diff --git a/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/main.kt b/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/main.kt
index 21d1a64e496..ecfc70fb0c9 100644
--- a/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/main.kt
+++ b/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/main.kt
@@ -381,6 +381,12 @@ internal fun buildNativeLibrary(
     val compilerOpts: List<String> = mutableListOf<String>().apply {
         addAll(def.config.compilerOpts)
         addAll(tool.defaultCompilerOpts)
+        // We compile with -O2 because Clang may insert inline asm in bitcode at -O0.
+        // It is undesirable in case of watchos_arm64 since we target armv7k
+        // for this target instead of arm64_32 because it is not supported in LLVM 8.
+        //
+        // Note that PCH and the *.c file should be compiled with the same optimization level.
+        add("-O2")
         addAll(additionalCompilerOpts)
         addAll(getCompilerFlagsForVfsOverlay(arguments.headerFilterPrefix.toTypedArray(), def))
         addAll(when (language) {