diff --git a/src/lib/icu/CaseFold.cxx b/src/lib/icu/CaseFold.cxx
index ed4552d1c..d34b1737b 100644
--- a/src/lib/icu/CaseFold.cxx
+++ b/src/lib/icu/CaseFold.cxx
@@ -45,7 +45,7 @@
 #include <string.h>
 
 AllocatedString<>
-IcuCaseFold(const char *src)
+IcuCaseFold(const char *src) noexcept
 try {
 #ifdef HAVE_ICU
 #if !CLANG_CHECK_VERSION(3,6)
diff --git a/src/lib/icu/CaseFold.hxx b/src/lib/icu/CaseFold.hxx
index 7d13a6e2a..bb5d5e76e 100644
--- a/src/lib/icu/CaseFold.hxx
+++ b/src/lib/icu/CaseFold.hxx
@@ -27,6 +27,6 @@ template<typename T> class AllocatedString;
 
 gcc_nonnull_all
 AllocatedString<char>
-IcuCaseFold(const char *src);
+IcuCaseFold(const char *src) noexcept;
 
 #endif