diff --git a/src/cgtop/cgtop.c b/src/cgtop/cgtop.c
index 1a73fb099d..c68b56568b 100644
--- a/src/cgtop/cgtop.c
+++ b/src/cgtop/cgtop.c
@@ -506,6 +506,10 @@ static int refresh(const char *root, Hashmap *a, Hashmap *b, unsigned iteration)
         return 0;
 }
 
+static const char *empty_to_slash(const char *p) {
+        return isempty(p) ? "/" : p;
+}
+
 static int group_compare(const void*a, const void *b) {
         const Group *x = *(Group**)a, *y = *(Group**)b;
 
@@ -515,9 +519,9 @@ static int group_compare(const void*a, const void *b) {
                  * recursive summing is off, since that is actually
                  * not accumulative for all children. */
 
-                if (path_startswith(y->path, x->path))
+                if (path_startswith(empty_to_slash(y->path), empty_to_slash(x->path)))
                         return -1;
-                if (path_startswith(x->path, y->path))
+                if (path_startswith(empty_to_slash(x->path), empty_to_slash(y->path)))
                         return 1;
         }
 
@@ -666,7 +670,7 @@ static void display(Hashmap *a) {
 
                 g = array[j];
 
-                path = isempty(g->path) ? "/" : g->path;
+                path = empty_to_slash(g->path);
                 ellipsized = ellipsize(path, path_columns, 33);
                 printf("%-*s", path_columns, ellipsized ?: path);