diff --git a/include/mimalloc-types.h b/include/mimalloc-types.h
index 016bb684..3a4f8f6b 100644
--- a/include/mimalloc-types.h
+++ b/include/mimalloc-types.h
@@ -132,7 +132,7 @@ typedef int32_t  mi_ssize_t;
 
 // Main tuning parameters for segment and page sizes
 // Sizes for 64-bit (usually divide by two for 32-bit)
-#define MI_SEGMENT_SLICE_SHIFT            (13 + MI_INTPTR_SHIFT)         // 64KiB  (32KiB on 32-bit)
+#define MI_SEGMENT_SLICE_SHIFT            (12 + MI_INTPTR_SHIFT)         // 64KiB  (32KiB on 32-bit)
 
 #if MI_INTPTR_SIZE > 4
 #define MI_SEGMENT_SHIFT                  (10 + MI_SEGMENT_SLICE_SHIFT)  // 64MiB
@@ -324,7 +324,7 @@ typedef enum mi_segment_kind_e {
 // is still tracked in fine-grained MI_COMMIT_SIZE chunks)
 // ------------------------------------------------------
 
-#define MI_MINIMAL_COMMIT_SIZE      (2*MI_MiB)
+#define MI_MINIMAL_COMMIT_SIZE      (MI_MiB)
 #define MI_COMMIT_SIZE              (MI_SEGMENT_SLICE_SIZE)              // 64KiB
 #define MI_COMMIT_MASK_BITS         (MI_SEGMENT_SIZE / MI_COMMIT_SIZE)  
 #define MI_COMMIT_MASK_FIELD_BITS    MI_SIZE_BITS