diff --git a/include/mimalloc-types.h b/include/mimalloc-types.h
index 8cd3a4c3..63549792 100644
--- a/include/mimalloc-types.h
+++ b/include/mimalloc-types.h
@@ -320,10 +320,15 @@ typedef enum mi_segment_kind_e {
 // the corresponding MI_COMMIT_SIZE area is committed.
 // The MI_COMMIT_SIZE must be a multiple of the slice
 // size. If it is equal we have the most fine grained 
-// decommit but setting it higher can be more efficient.
+// decommit (but setting it higher can be more efficient).
+// The MI_MINIMAL_COMMIT_SIZE is the minimal amount that will
+// be committed in one go which can be set higher than
+// MI_COMMIT_SIZE for efficiency (while the decommit mask
+// is still tracked in fine-grained MI_COMMIT_SIZE chunks)
 // ------------------------------------------------------
 
-#define MI_COMMIT_SIZE              (8*MI_SEGMENT_SLICE_SIZE)   
+#define MI_MINIMAL_COMMIT_SIZE      (16*MI_SEGMENT_SLICE_SIZE)           // 1MiB
+#define MI_COMMIT_SIZE              (MI_SEGMENT_SLICE_SIZE)
 #define MI_COMMIT_MASK_BITS         (MI_SEGMENT_SIZE / MI_COMMIT_SIZE)  
 #define MI_COMMIT_MASK_FIELD_BITS    MI_SIZE_BITS
 #define MI_COMMIT_MASK_FIELD_COUNT  (MI_COMMIT_MASK_BITS / MI_COMMIT_MASK_FIELD_BITS)
diff --git a/src/segment.c b/src/segment.c
index e8c80d29..0970046d 100644
--- a/src/segment.c
+++ b/src/segment.c
@@ -470,17 +470,20 @@ static void mi_segment_commit_mask(mi_segment_t* segment, bool conservative, uin
   if (p >= (uint8_t*)segment + segsize) return;
 
   size_t diff = (p - (uint8_t*)segment);
+  mi_assert_internal(diff + size <= segsize);
+
   size_t start;
   size_t end;
   if (conservative) {
+    // decommit conservative
     start = _mi_align_up(diff, MI_COMMIT_SIZE);
     end   = _mi_align_down(diff + size, MI_COMMIT_SIZE);
   }
   else {
+    // commit liberal
     start = _mi_align_down(diff, MI_COMMIT_SIZE);
-    end   = _mi_align_up(diff + size, MI_COMMIT_SIZE);
+    end   = _mi_align_up(diff + size, MI_MINIMAL_COMMIT_SIZE);
   }
-  mi_assert_internal(end <= segsize);
   if (end > segsize) {
     end = segsize;
   }