diff --git a/include/mimalloc-types.h b/include/mimalloc-types.h
index d44ecc18..399001c6 100644
--- a/include/mimalloc-types.h
+++ b/include/mimalloc-types.h
@@ -132,10 +132,10 @@ 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            (12 + MI_INTPTR_SHIFT)         // 32KiB  (32KiB on 32-bit)
+#define MI_SEGMENT_SLICE_SHIFT            (13 + MI_INTPTR_SHIFT)         // 64KiB  (32KiB on 32-bit)
 
 #if MI_INTPTR_SIZE > 4
-#define MI_SEGMENT_SHIFT                  (10 + MI_SEGMENT_SLICE_SHIFT)  // 32MiB
+#define MI_SEGMENT_SHIFT                  ( 9 + MI_SEGMENT_SLICE_SHIFT)  // 32MiB
 #else
 #define MI_SEGMENT_SHIFT                  ( 7 + MI_SEGMENT_SLICE_SHIFT)  // 4MiB on 32-bit
 #endif
@@ -325,7 +325,7 @@ 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      (16*MI_SEGMENT_SLICE_SIZE)           // 1MiB
 #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