diff --git a/icu4c/source/common/putil.c b/icu4c/source/common/putil.c
index 11ca52970a3..d6303aba939 100644
--- a/icu4c/source/common/putil.c
+++ b/icu4c/source/common/putil.c
@@ -825,6 +825,10 @@ u_setDataDirectory(const char *directory) {
     length=uprv_strlen(directory);
     newDataDir = (char *)uprv_malloc(length + 2);
     uprv_strcpy(newDataDir, directory);
+    if(newDataDir[length-1]!=U_FILE_SEP_CHAR) {
+        newDataDir[length++]=U_FILE_SEP_CHAR;
+        newDataDir[length] = 0;
+    }
 
     umtx_lock(NULL);
     if (gDataDirectory) {