diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 18d2beb89340a6deeb4e9cdb48cca5a27b23155d..42b968a85863041a98e393ec800a4c34cb1c1736 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -893,7 +893,7 @@ void ptep_zap_key(struct mm_struct *mm, unsigned long addr, pte_t *ptep);
 bool test_and_clear_guest_dirty(struct mm_struct *mm, unsigned long address);
 int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
 			  unsigned char key, bool nq);
-unsigned char get_guest_storage_key(struct mm_struct *mm, unsigned long addr);
+unsigned long get_guest_storage_key(struct mm_struct *mm, unsigned long addr);
 
 /*
  * Certain architectures need to do special things when PTEs
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 4324b87f93982f08552ecb86bb9c893431507427..2a23ca96f9c29bd9429a722d5fc8f7d69709629a 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -543,7 +543,7 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
 }
 EXPORT_SYMBOL(set_guest_storage_key);
 
-unsigned char get_guest_storage_key(struct mm_struct *mm, unsigned long addr)
+unsigned long get_guest_storage_key(struct mm_struct *mm, unsigned long addr)
 {
 	unsigned char key;
 	spinlock_t *ptl;