diff --git a/src/asm/jump_s390x_sysv_elf_gas.S b/src/asm/jump_s390x_sysv_elf_gas.S
index c2a578b..1dc5600 100644
--- a/src/asm/jump_s390x_sysv_elf_gas.S
+++ b/src/asm/jump_s390x_sysv_elf_gas.S
@@ -131,11 +131,11 @@ jump_fcontext:
 	ltg	%r2,GR_OFFSET(%r15)
 	jnz	use_return_slot
 
-	/* We restore a make_fcontext context.  Use the function
-	   argument slot in the context we just saved and allocate the
-	   register save area for the target function.  */
-	la	%r2,ARG_OFFSET(%r1)
-	aghi	%r15,-REG_SAVE_AREA_SIZE
+	/* We're restoring a context created by make_fcontext.
+	   Use the function argument slot in the current context
+	   and make sure it isn't deallocated. */
+	la	%r2,ARG_OFFSET(%r15)
+	aghi	%r15,-CONTEXT_SIZE
 
 use_return_slot:
 	/* Save the two fields in transfer_t.  When calling a
diff --git a/src/asm/make_s390x_sysv_elf_gas.S b/src/asm/make_s390x_sysv_elf_gas.S
index e7e2d5f..97778dd 100644
--- a/src/asm/make_s390x_sysv_elf_gas.S
+++ b/src/asm/make_s390x_sysv_elf_gas.S
@@ -71,7 +71,7 @@ r4 - The address of the context function
 
 make_fcontext:
 	.machine "z10"
-	/* Align the stack to an 8 byte boundary.  */
+	/* Align the stack to an 16 byte boundary.  */
 	nill    %r2,0xfff0
 
 	/* Allocate stack space for the context.  */
diff --git a/src/asm/ontop_s390x_sysv_elf_gas.S b/src/asm/ontop_s390x_sysv_elf_gas.S
index 709b3d6..fa7d112 100644
--- a/src/asm/ontop_s390x_sysv_elf_gas.S
+++ b/src/asm/ontop_s390x_sysv_elf_gas.S
@@ -82,6 +82,7 @@ created via make_fcontext.
 */
 
 ontop_fcontext:
+	.machine "z10"
 	/* Reserve stack space to store the current context.  */
 	aghi	%r15,-CONTEXT_SIZE