diff --git a/makefiles/libc/newlib.mk b/makefiles/libc/newlib.mk
index 916105657eff..89a515e3cbca 100644
--- a/makefiles/libc/newlib.mk
+++ b/makefiles/libc/newlib.mk
@@ -28,6 +28,10 @@ export LINKFLAGS += -lc
 
 # Search for Newlib include directories
 
+# Function that returns absolute path to directories that contain newlib.h
+# It returns the directory without trailing slash
+dir_contains_newlib_h = $(realpath $(dir $(wildcard $(addsuffix /newlib.h, $(1)))))
+
 # Try to search for newlib in the standard search path of the compiler for includes
 ifeq (,$(NEWLIB_INCLUDE_DIR))
   COMPILER_INCLUDE_PATHS := $(shell $(PREFIX)gcc -v -x c -E /dev/null 2>&1 | \
@@ -35,7 +39,7 @@ ifeq (,$(NEWLIB_INCLUDE_DIR))
                               -e '1,/\#include <...> search starts here:/d' \
                               -e '/End of search list./,$$d' \
                               -e 's/^ *//')
-  NEWLIB_INCLUDE_DIR := $(firstword $(realpath $(dir $(wildcard $(addsuffix /newlib.h, $(COMPILER_INCLUDE_PATHS))))))
+  NEWLIB_INCLUDE_DIR := $(firstword $(call dir_contains_newlib_h, $(COMPILER_INCLUDE_PATHS)))
 endif
 
 ifeq (,$(NEWLIB_INCLUDE_DIR))
@@ -63,13 +67,14 @@ ifeq (,$(NEWLIB_INCLUDE_DIR))
   # the patterns above. We use the -isystem gcc/clang argument to add the include
   # directories as system include directories, which means they will not be
   # searched until after all the project specific include directories (-I/path)
-  NEWLIB_INCLUDE_DIR := $(firstword $(realpath $(dir $(wildcard $(addsuffix /newlib.h, $(NEWLIB_INCLUDE_PATTERNS))))))
+  NEWLIB_INCLUDE_DIR := $(firstword $(call dir_contains_newlib_h, $(NEWLIB_INCLUDE_PATTERNS)))
 endif
 
 # If nothing was found we will try to fall back to searching for a cross-gcc in
 # the current PATH and use a relative path for the includes
 ifeq (,$(NEWLIB_INCLUDE_DIR))
-  NEWLIB_INCLUDE_DIR := $(realpath $(wildcard $(dir $(shell command -v $(PREFIX)gcc 2>/dev/null))/../$(TARGET_ARCH)/include))
+  GCC_RELATIVE_INCLUDE_PATH := $(dir $(shell command -v $(PREFIX)gcc 2>/dev/null))/../$(TARGET_ARCH)/include
+  NEWLIB_INCLUDE_DIR := $(call dir_contains_newlib_h, $(GCC_RELATIVE_INCLUDE_PATH))
 endif
 
 ifeq ($(TOOLCHAIN),llvm)
@@ -78,7 +83,7 @@ ifeq ($(TOOLCHAIN),llvm)
   # for the system being built.
   # We also add -nostdinc to avoid including the host system headers by mistake
   # in case some header is missing from the cross tool chain
-  NEWLIB_INCLUDES := -isystem $(NEWLIB_INCLUDE_DIR) -nostdinc
+  NEWLIB_INCLUDES := $(addprefix -isystem ,$(NEWLIB_INCLUDE_DIR)) -nostdinc
   NEWLIB_INCLUDES += $(addprefix -isystem ,$(realpath $(wildcard $(dir $(NEWLIB_INCLUDE_DIR))/usr/include)))
 
   # Newlib includes should go before GCC includes. This is especially important
@@ -90,10 +95,10 @@ ifeq ($(TOOLCHAIN),llvm)
 endif
 
 ifeq (1,$(USE_NEWLIB_NANO))
-  NEWLIB_NANO_INCLUDE_DIR ?= $(firstword $(wildcard $(NEWLIB_INCLUDE_DIR)/newlib-nano \
-                                                    $(NEWLIB_INCLUDE_DIR)/newlib/nano \
-                                                    $(NEWLIB_INCLUDE_DIR)/nano))
+  NEWLIB_NANO_INCLUDE_PATTERNS ?= $(addprefix $(NEWLIB_INCLUDE_DIR)/, newlib-nano newlib/nano nano)
+  NEWLIB_NANO_INCLUDE_DIR ?= $(firstword $(call dir_contains_newlib_h, $(NEWLIB_NANO_INCLUDE_PATTERNS)))
+
   # newlib-nano overrides newlib.h and its include dir should therefore go before
   # the regular system include dirs.
-  INCLUDES := -isystem $(NEWLIB_NANO_INCLUDE_DIR) $(INCLUDES)
+  INCLUDES := $(addprefix -isystem ,$(NEWLIB_NANO_INCLUDE_DIR)) $(INCLUDES)
 endif