diff --git a/Arduino.mk b/Arduino.mk
index a352628..42dfef0 100644
--- a/Arduino.mk
+++ b/Arduino.mk
@@ -279,6 +279,12 @@ else
     $(call show_config_variable,ARDUINO_DIR,[USER])
 endif
 
+ifeq ($(CURRENT_OS),WINDOWS)
+    ifneq ($(shell echo $(ARDUINO_DIR) | egrep '^(/|[a-zA-Z]:\\)'),)
+        echo $(error On Windows, ARDUINO_DIR must be a relative path)
+    endif
+endif
+
 ########################################################################
 # Default TARGET to pwd (ex Daniele Vergini)
 
diff --git a/chipKIT.mk b/chipKIT.mk
index 19a4a4a..06d85e3 100644
--- a/chipKIT.mk
+++ b/chipKIT.mk
@@ -47,6 +47,12 @@ else
     $(call show_config_variable,MPIDE_DIR,[USER])
 endif
 
+ifeq ($(CURRENT_OS),WINDOWS)
+    ifneq ($(shell echo $(ARDUINO_DIR) | egrep '^(/|[a-zA-Z]:\\)'),)
+        echo $(error On Windows, MPIDE_DIR must be a relative path)
+    endif
+endif
+
 ifndef MPIDE_PREFERENCES_PATH
     AUTO_MPIDE_PREFERENCES_PATH := $(firstword \
         $(call dir_if_exists,$(HOME)/.mpide/preferences.txt) \