diff --git a/cores/arduino/Arduino.h b/cores/arduino/Arduino.h
index ff3938463..ba544f3eb 100644
--- a/cores/arduino/Arduino.h
+++ b/cores/arduino/Arduino.h
@@ -17,6 +17,9 @@
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
 
+#if ARDUINO_LIBRARY_DISCOVERY_PHASE == 1
+#define ARDUINO_LIB_DISCOVERY_PHASE
+#endif
 #if !defined(Arduino_h) && !defined(ARDUINO_LIB_DISCOVERY_PHASE)
 #define Arduino_h
 
diff --git a/platform.txt b/platform.txt
index 339c18371..f36367e4f 100644
--- a/platform.txt
+++ b/platform.txt
@@ -52,6 +52,10 @@ compiler.ar.extra_flags=
 compiler.objcopy.eep.extra_flags=
 compiler.elf2hex.extra_flags=
 
+# {build.library_discovery_phase} is set to 1 by the builder during library discovery.
+# (this is available since arduino-builder>=1.5.5, keeping the default here for backward compatiblity)
+build.library_discovery_phase=0
+build.library_discovery_phase_flag=-DARDUINO_LIBRARY_DISCOVERY_PHASE={build.library_discovery_phase}
 
 # USB Flags
 # ---------
@@ -67,10 +71,10 @@ build.zip.pattern={recipe.size.pattern}
 # -----------------------
 
 ## Compile c files
-recipe.c.o.pattern="{compiler.path}{compiler.c.cmd}" {compiler.c.flags} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch}  {build.extra_flags} {compiler.c.extra_flags} "-I{build.core.path}/api/deprecated" {includes} "-iprefix{build.core.path}" "@{compiler.mbed.includes}" -o "{object_file}" "{source_file}"
+recipe.c.o.pattern="{compiler.path}{compiler.c.cmd}" {compiler.c.flags} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {build.library_discovery_phase_flag} {build.extra_flags} {compiler.c.extra_flags} "-I{build.core.path}/api/deprecated" {includes} "-iprefix{build.core.path}" "@{compiler.mbed.includes}" -o "{object_file}" "{source_file}"
 
 ## Compile c++ files
-recipe.cpp.o.pattern="{compiler.path}{compiler.cpp.cmd}" {compiler.cpp.flags} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {includes} {build.extra_flags} {compiler.cpp.extra_flags} "-I{build.core.path}/api/deprecated" "-iprefix{build.core.path}" "@{compiler.mbed.includes}" "{source_file}" -o "{object_file}"
+recipe.cpp.o.pattern="{compiler.path}{compiler.cpp.cmd}" {compiler.cpp.flags} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {build.library_discovery_phase_flag} {includes} {build.extra_flags} {compiler.cpp.extra_flags} "-I{build.core.path}/api/deprecated" "-iprefix{build.core.path}" "@{compiler.mbed.includes}" "{source_file}" -o "{object_file}"
 
 ## Compile asm files
 recipe.S.o.pattern="{compiler.path}{compiler.S.cmd}" {compiler.S.flags} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {includes} {build.extra_flags} {compiler.cpp.extra_flags} "-I{build.core.path}/api/deprecated" "-iprefix{build.core.path}" "@{compiler.mbed.includes}" "{source_file}" -o "{object_file}"