Index: uspace/lib/libc/arch/sparc64/include/fibril.h
===================================================================
--- uspace/lib/libc/arch/sparc64/include/fibril.h	(revision ec8b0dac0a89d85fb1256e7e6a702141cc630506)
+++ uspace/lib/libc/arch/sparc64/include/fibril.h	(revision 716fb9d713ceb210b9824bd965bbd54b4a054b9f)
@@ -40,5 +40,5 @@
 #include <align.h>
 
-#define SP_DELTA	STACK_WINDOW_SAVE_AREA_SIZE
+#define SP_DELTA	(STACK_WINDOW_SAVE_AREA_SIZE + STACK_ARG_SAVE_AREA_SIZE)
 
 #ifdef context_set
Index: uspace/lib/libc/arch/sparc64/include/stack.h
===================================================================
--- uspace/lib/libc/arch/sparc64/include/stack.h	(revision ec8b0dac0a89d85fb1256e7e6a702141cc630506)
+++ uspace/lib/libc/arch/sparc64/include/stack.h	(revision 716fb9d713ceb210b9824bd965bbd54b4a054b9f)
@@ -46,4 +46,9 @@
 #define STACK_WINDOW_SAVE_AREA_SIZE	(16 * STACK_ITEM_SIZE)
 
+/*
+ * Six extended words for first six arguments.
+ */
+#define STACK_ARG_SAVE_AREA_SIZE		(6 * STACK_ITEM_SIZE)
+
 /**
  * By convention, the actual top of the stack is %sp + STACK_BIAS.