diff --git a/CMakeLists.txt b/CMakeLists.txt
index 579050b3..56732b81 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -457,7 +457,7 @@ function(add_picolibc directory variant target_triple flags qemu_params variant_
         INSTALL_DIR "${LLVM_BINARY_DIR}/${directory}"
         PREFIX picolibc/${variant}
         DEPENDS clang lld llvm-ar llvm-config llvm-nm llvm-ranlib llvm-strip
-        CONFIGURE_COMMAND ${MESON_EXECUTABLE} -Dincludedir=include -Dlibdir=lib -Dspecsdir=none --prefix <INSTALL_DIR> --cross-file <BINARY_DIR>/meson-cross-build.txt ${picolibc_SOURCE_DIR}
+        CONFIGURE_COMMAND ${MESON_EXECUTABLE} -Dincludedir=include -Dlibdir=lib -Dio-long-double=true -Dspecsdir=none --prefix <INSTALL_DIR> --cross-file <BINARY_DIR>/meson-cross-build.txt ${picolibc_SOURCE_DIR}
         BUILD_COMMAND ninja
         INSTALL_COMMAND ${MESON_EXECUTABLE} install ${MESON_INSTALL_QUIET}
         USES_TERMINAL_CONFIGURE TRUE