--- source/tools/genrb/rbutil.c
+++ source/tools/genrb/rbutil.c
@@ -30,7 +30,12 @@
 get_dirname(char *dirname,
             const char *filename)
 {
-  const char *lastSlash = uprv_strrchr(filename, U_FILE_SEP_CHAR) + 1;
+  const char *lastSlash = uprv_strrchr(filename, U_FILE_SEP_CHAR);
+  if(lastSlash == NULL) {
+    lastSlash = filename;
+  } else {
+     ++lastSlash;
+  }
 
   if(lastSlash>filename) {
     uprv_strncpy(dirname, filename, (lastSlash - filename));
@@ -46,7 +51,12 @@
              const char *filename)
 {
   /* strip off any leading directory portions */
-  const char *lastSlash = uprv_strrchr(filename, U_FILE_SEP_CHAR) + 1;
+  const char *lastSlash = uprv_strrchr(filename, U_FILE_SEP_CHAR);
+  if(lastSlash == NULL) {
+    lastSlash = filename;
+  } else {
+     ++lastSlash;
+  }
   char *lastDot;
 
   if(lastSlash>filename) {