diff --git a/docs/Doxyfile b/docs/Doxyfile
index a1bd960..ea22337 100644
--- a/docs/Doxyfile
+++ b/docs/Doxyfile
@@ -1638,6 +1638,7 @@
     "__attribute__(x)=" \
     __ANDROID__ \
     __BIONIC__ \
+    "U_IN_DOXYGEN=1" \ # Required by the ICU4C module only
 
 # If the MACRO_EXPANSION and EXPAND_ONLY_PREDEF tags are set to YES then
 # this tag can be used to specify a list of macro names that should be expanded.