--- misc/icu/source/common/unicode/
+++ misc/build/icu/source/common/unicode/utf16.h
@@ -316,6 +316,7 @@
         (s)[(i)++]=(uint16_t)(((c)&0x3ff)|0xdc00); \
     } else /* c>0x10ffff or not enough space */ { \
         (isError)=TRUE; \
+        (void)(isError); \
     } \
 }