diff --git a/AK/Demangle.h b/AK/Demangle.h
index bc422f5f6be..722c32b4773 100644
--- a/AK/Demangle.h
+++ b/AK/Demangle.h
@@ -28,7 +28,7 @@
 
 #include <AK/String.h>
 
-#ifndef SERENITY_LIBC_BUILD
+#ifndef BUILDING_SERENITY_TOOLCHAIN
 #include <cxxabi.h>
 #endif
 
@@ -36,7 +36,7 @@ namespace AK {
 
 inline String demangle(const StringView& name)
 {
-#ifdef SERENITY_LIBC_BUILD
+#ifdef BUILDING_SERENITY_TOOLCHAIN
     return name;
 #else
     int status = 0;
diff --git a/Libraries/LibC/Makefile b/Libraries/LibC/Makefile
index 067a4d73c64..71acff8ace0 100644
--- a/Libraries/LibC/Makefile
+++ b/Libraries/LibC/Makefile
@@ -81,7 +81,7 @@ crtn.o: crtin.ao
 
 EXTRA_CLEAN = crt0.d crt0.o
 
-DEFINES = -DSERENITY_LIBC_BUILD
+DEFINES = -DSERENITY_LIBC_BUILD $(EXTRA_LIBC_DEFINES)
 
 LIBRARY = libc.a
 
diff --git a/Toolchain/BuildIt.sh b/Toolchain/BuildIt.sh
index 66b66c76b8a..6eb6c3a4c9f 100755
--- a/Toolchain/BuildIt.sh
+++ b/Toolchain/BuildIt.sh
@@ -148,7 +148,7 @@ pushd "$DIR/Build/"
         "$MAKE" install-gcc install-target-libgcc || exit 1
 
         echo "XXX serenity libc and libm"
-        ( cd "$DIR/../Libraries/LibC/" && "$MAKE" clean && "$MAKE" && "$MAKE" install )
+        ( cd "$DIR/../Libraries/LibC/" && "$MAKE" clean && "$MAKE" EXTRA_LIBC_DEFINES="-DBUILDING_SERENITY_TOOLCHAIN" && "$MAKE" install )
         ( cd "$DIR/../Libraries/LibM/" && "$MAKE" clean && "$MAKE" && "$MAKE" install )
 
         echo "XXX build libstdc++"