diff --git a/doc/internal/gc.md b/doc/internal/gc.md
index cf221c6a5..1d355fcb3 100644
--- a/doc/internal/gc.md
+++ b/doc/internal/gc.md
@@ -131,7 +131,9 @@ limit = (GC_STEP_SIZE / 100) * step_ratio
 ```
 
 With default `step_ratio = 200` and `GC_STEP_SIZE = 1024`, the
-limit is 2048 objects per step.
+limit is 2048 objects per step. After each step, `gc_debt` is
+decremented by the actual number of objects processed, so larger
+steps repay more debt.
 
 When the gray stack is exhausted, the final marking phase re-marks
 the arena and global variables to catch objects created during
diff --git a/src/gc.c b/src/gc.c
index 24feb72a3..283d1dcdb 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -1332,7 +1332,7 @@ incremental_gc_step(mrb_state *mrb, mrb_gc *gc)
       break;
   }
 
-  gc->gc_debt -= (mrb_int)GC_STEP_SIZE;
+  gc->gc_debt -= (mrb_int)result;
 }
 
 static void