diff --git a/src/libImaging/Imaging.h b/src/libImaging/Imaging.h
index 75a2fa0a3..b2fe5e1d8 100644
--- a/src/libImaging/Imaging.h
+++ b/src/libImaging/Imaging.h
@@ -201,7 +201,7 @@ extern struct ImagingMemoryArena ImagingArenas[IMAGING_ARENAS_COUNT + 1];
  * statically-allocated. This is necessary to properly handle stats.
  */
 #define IMAGING_ARENAS_FOREACH(arena) \
-    for ((arena) = &ImagingArenas[0]; (arena)->alignment >= 0; ++(arena))
+    for ((arena) = &ImagingArenas[0]; (arena)->index >= 0; ++(arena))
 #else
 /* In this case we either have the GIL or do not have thread-local storage, in
  * which case we will only allocate a single arena.
diff --git a/src/libImaging/Storage.c b/src/libImaging/Storage.c
index 6f3445171..620f106ce 100644
--- a/src/libImaging/Storage.c
+++ b/src/libImaging/Storage.c
@@ -282,7 +282,7 @@ struct ImagingMemoryArena ImagingArenas[IMAGING_ARENAS_COUNT + 1] = {
     {1, IMAGING_ARENA_BLOCK_SIZE, 0, 0, NULL, 0, 0, 0, 0, 0, 5, {0}},
     {1, IMAGING_ARENA_BLOCK_SIZE, 0, 0, NULL, 0, 0, 0, 0, 0, 6, {0}},
     {1, IMAGING_ARENA_BLOCK_SIZE, 0, 0, NULL, 0, 0, 0, 0, 0, 7, {0}},
-    {-1},
+    {1, IMAGING_ARENA_BLOCK_SIZE, 0, 0, NULL, 0, 0, 0, 0, 0, -1, {0}},
 };
 
 /* Get a pointer to the correct arena for this context. In this case where we