diff --git a/ce/edit.c b/ce/edit.c
index 55d90fe..3f56d99 100644
--- a/ce/edit.c
+++ b/ce/edit.c
@@ -283,10 +283,7 @@ void edit_start (const char* file_path, const char* text) {
             struct edit_line* next_line = list_entry (next, struct edit_line, lines_link);
             size_t next_len = gapbuffer_length (&next_line->gb);
 
-            for (size_t i = 0; i < next_len; i++) {
-              char chr = gapbuffer_at (&next_line->gb, i);
-              gapbuffer_insert (&wrealloc, NULL, &editor.current_line->gb, chr);
-            }
+            gapbuffer_concat (&wrealloc, NULL, &editor.current_line->gb, &next_line->gb);
 
             list_remove (editor.lines, &next_line->lines_link);
             free (next_line->gb.buffer);
diff --git a/ce/gapbuffer.c b/ce/gapbuffer.c
index 3537bc3..6a4945d 100644
--- a/ce/gapbuffer.c
+++ b/ce/gapbuffer.c
@@ -113,9 +113,25 @@ char* gapbuffer_string_at (gb_malloc_func_t mallocfn, void* ctx, struct gapbuffe
   return res;
 }
 
-char gapbuffer_at (struct gapbuffer* gb, size_t index) {
-  if (index < gb->gap_start)
-    return gb->buffer[index];
-  else
-    return gb->buffer[index + (gb->gap_end - gb->gap_start)];
+void gapbuffer_concat (gb_realloc_func_t reallocfn, void* ctx, struct gapbuffer* dest,
+                       struct gapbuffer* src) {
+  size_t src_len = gapbuffer_length (src);
+
+  if (src_len == 0)
+    return;
+
+  while ((dest->gap_end - dest->gap_start) < src_len)
+    gapbuffer_grow (reallocfn, ctx, dest);
+
+  gapbuffer_move (dest, gapbuffer_length (dest));
+
+  size_t part1_len = src->gap_start;
+  memcpy (dest->buffer + dest->gap_start, src->buffer, part1_len);
+  dest->gap_start += part1_len;
+
+  size_t part2_len = src->size - src->gap_end;
+  if (part2_len > 0) {
+    memcpy (dest->buffer + dest->gap_start, src->buffer + src->gap_end, part2_len);
+    dest->gap_start += part2_len;
+  }
 }
diff --git a/ce/gapbuffer.h b/ce/gapbuffer.h
index 1401f8c..da94a23 100644
--- a/ce/gapbuffer.h
+++ b/ce/gapbuffer.h
@@ -33,6 +33,7 @@ size_t gapbuffer_length (struct gapbuffer* gb);
 
 char* gapbuffer_string_at (gb_malloc_func_t mallocfn, void* ctx, struct gapbuffer* gb, size_t pos);
 
-char gapbuffer_at (struct gapbuffer* gb, size_t index);
+void gapbuffer_concat (gb_realloc_func_t reallocfn, void* ctx, struct gapbuffer* dest,
+                       struct gapbuffer* src);
 
 #endif // _GAPBUFFER_H