diff --git a/icu4c/source/data/makedata.mak b/icu4c/source/data/makedata.mak
index 7f6b5dc8431..bb6feb53680 100644
--- a/icu4c/source/data/makedata.mak
+++ b/icu4c/source/data/makedata.mak
@@ -26,9 +26,13 @@ UNICODE_VERSION=4
 !ENDIF
 !MESSAGE ICU data make path is $(ICUMAKE)
 
-ICUBLD=$(ICUMAKE)\out\build
 ICUOUT=$(ICUMAKE)\out
 
+# need to nuke \\ for .NET...
+ICUOUT=$(ICUOUT:\\=\)
+
+ICUBLD=$(ICUOUT)\build
+
 # ICUDT
 #  the prefix "icudt21_" for use in filenames
 ICUPKG=$(U_ICUDATA_NAME)$(U_ICUDATA_ENDIAN_SUFFIX)