diff --git a/konan/konan.properties b/konan/konan.properties
index f569b1e352a..358ba48b5b6 100644
--- a/konan/konan.properties
+++ b/konan/konan.properties
@@ -114,7 +114,10 @@ targetSysRoot.ios_arm64 = target-sysroot-9-ios_arm64
 clangFlags.ios_arm64 = -cc1 -emit-obj -disable-llvm-passes -x ir
 clangNooptFlags.ios_arm64 = -O1
 clangOptFlags.ios_arm64 = -O3
-clangDebugFlags.ios_arm64 = -O0
+# We force LLVM to use SelectionDAG because fast isel may miscompile sign extension.
+# Related:
+# https://github.com/JetBrains/kotlin-native/issues/3290
+clangDebugFlags.ios_arm64 = -O0 -mllvm -fast-isel=false -mllvm -global-isel=false
 clangDynamicFlags.ios_arm64 =
 
 linkerNoDebugFlags.ios_arm64 = -S
@@ -192,7 +195,7 @@ targetSysRoot.tvos_arm64 = target-sysroot-9-tvos_arm64
 clangFlags.tvos_arm64 = -cc1 -emit-obj -disable-llvm-passes -x ir
 clangNooptFlags.tvos_arm64 = -O1
 clangOptFlags.tvos_arm64 = -O3
-clangDebugFlags.tvos_arm64 = -O0
+clangDebugFlags.tvos_arm64 = -O0 -mllvm -fast-isel=false -mllvm -global-isel=false
 clangDynamicFlags.tvos_arm64 =
 
 linkerNoDebugFlags.tvos_arm64 = -S