diff --git a/icu4c/source/tools/toolutil/package.cpp b/icu4c/source/tools/toolutil/package.cpp
index e8d7bf7d1ec..bd0ea80ebe5 100644
--- a/icu4c/source/tools/toolutil/package.cpp
+++ b/icu4c/source/tools/toolutil/package.cpp
@@ -609,6 +609,7 @@ Package::readPackage(const char *filename) {
                 exit(U_INVALID_FORMAT_ERROR);
             }
             memcpy(pkgPrefix, s, prefixLength);
+            pkgPrefix[prefixLength]=0;
             memcpy(prefix, s, ++prefixLength);  // include the /
         } else {
             // Use the package basename as prefix.