diff --git a/src/lib/lwp/arch.c b/src/lib/lwp/arch.c
index 9c70d5ea..992629ab 100644
--- a/src/lib/lwp/arch.c
+++ b/src/lib/lwp/arch.c
@@ -77,15 +77,16 @@ lwpNewContext(struct lwpProc *newp, int stacksz)
 	free(s);
 	return -1;
     }
-    newp->context.uc_stack.ss_sp = newp->ustack;
-    newp->context.uc_stack.ss_size = newp->usize;
 #ifdef MAKECONTEXT_SP_HIGH
     /*
      * Known systems that are broken that way: Solaris prior to 10,
      * IRIX.
      */
-    newp->context.uc_stack.ss_sp += stacksz - 8;
+    newp->context.uc_stack.ss_sp = newp->ustack + stacksz - 8;
+#else
+    newp->context.uc_stack.ss_sp = newp->ustack;
 #endif
+    newp->context.uc_stack.ss_size = newp->usize;
     newp->context.uc_stack.ss_flags = 0;
     newp->context.uc_link = NULL;
     makecontext(&newp->context, lwpEntryPoint, 0);