diff --git a/examples/simple/Makefile b/examples/simple/Makefile
index 970a865..b503f1b 100644
--- a/examples/simple/Makefile
+++ b/examples/simple/Makefile
@@ -3,7 +3,7 @@
 
 # Compiler flags to enable all warnings & debug info
 CFLAGS = -Wall -Werror -g -O0
-CFLAGS += -I$(NANOPB_DIR)
+CFLAGS += "-I$(NANOPB_DIR)"
 
 # C source code files that are required
 CSRC  = simple.c                   # The main program
diff --git a/extra/nanopb.mk b/extra/nanopb.mk
index 8be2929..279515f 100644
--- a/extra/nanopb.mk
+++ b/extra/nanopb.mk
@@ -2,7 +2,7 @@
 # .pb.c and .pb.h files out of .proto, as well the path to nanopb core.
 
 # Path to the nanopb root directory
-NANOPB_DIR := $(abspath $(dir $(lastword $(MAKEFILE_LIST)))../)
+NANOPB_DIR := $(patsubst %/,%,$(dir $(patsubst %/,%,$(dir $(lastword $(MAKEFILE_LIST))))))
 
 # Files for the nanopb core
 NANOPB_CORE = $(NANOPB_DIR)/pb_encode.c $(NANOPB_DIR)/pb_decode.c $(NANOPB_DIR)/pb_common.c
@@ -25,9 +25,9 @@
 	# Source only or git checkout
 	PROTOC_OPTS =
 	ifdef WINDOWS
-	    PROTOC = python "$(NANOPB_DIR)/generator/protoc"
+	    PROTOC = python $(NANOPB_DIR)/generator/protoc
 	else
-	    PROTOC = "$(NANOPB_DIR)/generator/protoc"
+	    PROTOC = $(NANOPB_DIR)/generator/protoc
 	endif
 endif