diff --git a/makefiles/nuttx.mk b/makefiles/nuttx.mk
index 5186dc3efe..346735a02a 100644
--- a/makefiles/nuttx.mk
+++ b/makefiles/nuttx.mk
@@ -64,8 +64,8 @@ LDSCRIPT		+= $(NUTTX_EXPORT_DIR)build/ld.script
 # Add directories from the NuttX export to the relevant search paths
 #
 INCLUDE_DIRS		+= $(NUTTX_EXPORT_DIR)include \
-			+= $(NUTTX_EXPORT_DIR)arch/chip \
-			+= $(NUTTX_EXPORT_DIR)arch/common
+			   $(NUTTX_EXPORT_DIR)arch/chip \
+			   $(NUTTX_EXPORT_DIR)arch/common
 
 LIB_DIRS		+= $(NUTTX_EXPORT_DIR)libs
 LIBS			+= -lapps -lnuttx