diff --git a/vm_core.h b/vm_core.h
index 73b552edd3..b25c68125c 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -585,8 +585,12 @@ typedef struct rb_vm_struct {
 
 #define RUBY_VM_FIBER_VM_STACK_SIZE           (  16 * 1024 * sizeof(VALUE)) /*   64 KB or  128 KB */
 #define RUBY_VM_FIBER_VM_STACK_SIZE_MIN       (   2 * 1024 * sizeof(VALUE)) /*    8 KB or   16 KB */
-#define RUBY_VM_FIBER_MACHINE_STACK_SIZE      (  64 * 1024 * sizeof(VALUE)) /*  256 KB or  512 KB */
+#define RUBY_VM_FIBER_MACHINE_STACK_SIZE      (  64 * 1024 * sizeof(VALUE)) /*  256 KB or  512 KB */ 
+#if defined(__powerpc64__)
+#define RUBY_VM_FIBER_MACHINE_STACK_SIZE_MIN  (  32 * 1024 * sizeof(VALUE)) /*   128 KB or  256 KB */
+#else
 #define RUBY_VM_FIBER_MACHINE_STACK_SIZE_MIN  (  16 * 1024 * sizeof(VALUE)) /*   64 KB or  128 KB */
+#endif
 
 /* optimize insn */
 #define INTEGER_REDEFINED_OP_FLAG (1 << 0)