diff --git a/Makefile b/Makefile
index 7fbfddcb..2f89585e 100644
--- a/Makefile
+++ b/Makefile
@@ -175,7 +175,7 @@ $(LLVM_BUILDDIR): $(LLVM_BUILDDIR)/build.ninja
 wasi-libc: lib/wasi-libc/sysroot/lib/wasm32-wasi/libc.a
 lib/wasi-libc/sysroot/lib/wasm32-wasi/libc.a:
 	@if [ ! -e lib/wasi-libc/Makefile ]; then echo "Submodules have not been downloaded. Please download them using:\n  git submodule update --init"; exit 1; fi
-	cd lib/wasi-libc && make -j4 WASM_CC=$(CLANG) WASM_AR=$(LLVM_AR) WASM_NM=$(LLVM_NM)
+	cd lib/wasi-libc && make -j4 WASM_CFLAGS="-O2 -g -DNDEBUG" WASM_CC=$(CLANG) WASM_AR=$(LLVM_AR) WASM_NM=$(LLVM_NM)
 
 
 # Build the Go compiler.
diff --git a/lib/wasi-libc b/lib/wasi-libc
index 215adc8a..ad513341 160000
--- a/lib/wasi-libc
+++ b/lib/wasi-libc
@@ -1 +1 @@
-Subproject commit 215adc8ac9f91eb055311acc72683fd2eb1ae15a
+Subproject commit ad5133410f66b93a2381db5b542aad5e0964db96