diff --git a/commit-slab-decl.h b/commit-slab-decl.h
index adc7b46c83..286164b7e2 100644
--- a/commit-slab-decl.h
+++ b/commit-slab-decl.h
@@ -32,6 +32,7 @@ struct slabname {							\
 void init_ ##slabname## _with_stride(struct slabname *s, unsigned stride); \
 void init_ ##slabname(struct slabname *s);				\
 void clear_ ##slabname(struct slabname *s);				\
+void deep_clear_ ##slabname(struct slabname *s, void (*free_fn)(elemtype *ptr)); \
 elemtype *slabname## _at_peek(struct slabname *s, const struct commit *c, int add_if_missing); \
 elemtype *slabname## _at(struct slabname *s, const struct commit *c);	\
 elemtype *slabname## _peek(struct slabname *s, const struct commit *c)
diff --git a/commit-slab-impl.h b/commit-slab-impl.h
index 5c0eb91a5d..557738df27 100644
--- a/commit-slab-impl.h
+++ b/commit-slab-impl.h
@@ -38,6 +38,19 @@ scope void clear_ ##slabname(struct slabname *s)			\
 	FREE_AND_NULL(s->slab);						\
 }									\
 									\
+scope void deep_clear_ ##slabname(struct slabname *s, void (*free_fn)(elemtype *)) \
+{									\
+	unsigned int i;							\
+	for (i = 0; i < s->slab_count; i++) {				\
+		unsigned int j;						\
+		if (!s->slab[i])					\
+			continue;					\
+		for (j = 0; j < s->slab_size; j++)			\
+			free_fn(&s->slab[i][j * s->stride]);		\
+	}								\
+	clear_ ##slabname(s);						\
+}									\
+									\
 scope elemtype *slabname## _at_peek(struct slabname *s,			\
 						  const struct commit *c, \
 						  int add_if_missing)   \
diff --git a/commit-slab.h b/commit-slab.h
index 05b3f2804e..8e72a30536 100644
--- a/commit-slab.h
+++ b/commit-slab.h
@@ -47,6 +47,16 @@
  *
  *   Call this function before the slab falls out of scope to avoid
  *   leaking memory.
+ *
+ * - void deep_clear_indegree(struct indegree *, void (*free_fn)(int*))
+ *
+ *   Empties the slab, similar to clear_indegree(), but in addition it
+ *   calls the given 'free_fn' for each slab entry to release any
+ *   additional memory that might be owned by the entry (but not the
+ *   entry itself!).
+ *   Note that 'free_fn' might be called even for entries for which no
+ *   indegree_at() call has been made; in this case 'free_fn' is invoked
+ *   with a pointer to a zero-initialized location.
  */
 
 #define define_commit_slab(slabname, elemtype) \
diff --git a/shallow.c b/shallow.c
index 7fd04afed1..c4ac8a7327 100644
--- a/shallow.c
+++ b/shallow.c
@@ -84,6 +84,10 @@ int is_repository_shallow(struct repository *r)
  * supports a "valid" flag.
  */
 define_commit_slab(commit_depth, int *);
+static void free_depth_in_slab(int **ptr)
+{
+	FREE_AND_NULL(*ptr);
+}
 struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
 		int shallow_flag, int not_shallow_flag)
 {
@@ -150,15 +154,7 @@ struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
 			}
 		}
 	}
-	for (i = 0; i < depths.slab_count; i++) {
-		int j;
-
-		if (!depths.slab[i])
-			continue;
-		for (j = 0; j < depths.slab_size; j++)
-			free(depths.slab[i][j]);
-	}
-	clear_commit_depth(&depths);
+	deep_clear_commit_depth(&depths, free_depth_in_slab);
 
 	return result;
 }