diff --git a/lsm/src/_include/lsm/store_internal.h b/lsm/src/_include/lsm/store_internal.h
index afbd4f3..f356bd4 100644
--- a/lsm/src/_include/lsm/store_internal.h
+++ b/lsm/src/_include/lsm/store_internal.h
@@ -10,6 +10,7 @@
 
 #define LSM_DB_FILE_NAME "lsm.db"
 #define LSM_IDX_FILE_NAME "lsm.idx"
+#define LSM_DATA_FILE_SUFFIX ".data"
 
 typedef struct lsm_attr {
   uint8_t type;
@@ -129,4 +130,15 @@ lsm_error lsm_entry_disk_remove(lsm_entry_handle *handle);
  */
 lsm_error lsm_entry_disk_update(lsm_entry_handle *handle);
 
+/**
+ * Return the length of the path to this entry's data file
+ */
+uint64_t lsm_entry_data_path_len(lsm_entry_handle *handle);
+
+/**
+ * Fill in the entry's data file path in the provided buffer. Use
+ * `lsm_entry_data_path_len` to allocate an appropriately-sized buffer
+ */
+void lsm_entry_data_path(char *buf, lsm_entry_handle *handle);
+
 #endif
diff --git a/lsm/src/store/lsm_store.c b/lsm/src/store/lsm_store.c
index 57eacb7..f93e289 100644
--- a/lsm/src/store/lsm_store.c
+++ b/lsm/src/store/lsm_store.c
@@ -174,11 +174,10 @@ lsm_error lsm_entry_data_append(lsm_entry_handle *handle, lsm_str *data) {
 
   // Entries don't open their file unless needed
   if (handle->f == NULL) {
-    char path[handle->store->data_path->len + entry->key->len + 2];
-    sprintf(path, "%s/%s", lsm_str_ptr(handle->store->data_path),
-            lsm_str_ptr(entry->key));
+    char data_path[lsm_entry_data_path_len(handle) + 1];
+    lsm_entry_data_path(data_path, handle);
 
-    FILE *f = fopen(path, "ab");
+    FILE *f = fopen(data_path, "ab");
 
     if (f == NULL) {
       return lsm_error_failed_io;
@@ -213,11 +212,10 @@ lsm_error lsm_entry_data_read(uint64_t *out, char *buf,
 
   // Entries don't open their file unless needed
   if (handle->f == NULL) {
-    char path[handle->store->data_path->len + entry->key->len + 2];
-    sprintf(path, "%s/%s", lsm_str_ptr(handle->store->data_path),
-            lsm_str_ptr(entry->key));
+    char data_path[lsm_entry_data_path_len(handle) + 1];
+    lsm_entry_data_path(data_path, handle);
 
-    FILE *f = fopen(path, "rb");
+    FILE *f = fopen(data_path, "rb");
 
     if (f == NULL) {
       return lsm_error_failed_io;
diff --git a/lsm/src/store/lsm_store_entry.c b/lsm/src/store/lsm_store_entry.c
index fd55624..a9c0ade 100644
--- a/lsm/src/store/lsm_store_entry.c
+++ b/lsm/src/store/lsm_store_entry.c
@@ -227,3 +227,25 @@ lsm_error lsm_entry_attr_insert_uint8_t(lsm_entry_handle *handle, uint8_t type,
 uint64_t lsm_entry_data_len(lsm_entry_handle *handle) {
   return handle->wrapper->entry->data_len;
 }
+
+uint64_t lsm_entry_data_path_len(lsm_entry_handle *handle) {
+  // [data path]/[entry key][data file suffix]
+  return lsm_str_len(handle->store->data_path) +
+         lsm_str_len(handle->wrapper->entry->key) +
+         strlen(LSM_DATA_FILE_SUFFIX) + 1;
+}
+void lsm_entry_data_path(char *buf, lsm_entry_handle *handle) {
+  lsm_str *data_path = handle->store->data_path;
+  lsm_str *key = handle->wrapper->entry->key;
+
+  memcpy(buf, lsm_str_ptr(data_path), lsm_str_len(data_path));
+
+  uint64_t index = lsm_str_len(data_path);
+  buf[index] = '/';
+
+  index += 1;
+  memcpy(&buf[index], lsm_str_ptr(key), lsm_str_len(key));
+
+  index += lsm_str_len(key);
+  strcpy(&buf[index], LSM_DATA_FILE_SUFFIX);
+}