diff --git a/include/libssh/fe25519.h b/include/libssh/fe25519.h
index e959912e..438d85db 100644
--- a/include/libssh/fe25519.h
+++ b/include/libssh/fe25519.h
@@ -39,7 +39,7 @@ void fe25519_unpack(fe25519 *r, const unsigned char x[32]);
 
 void fe25519_pack(unsigned char r[32], const fe25519 *x);
 
-int fe25519_iszero(const fe25519 *x);
+uint32_t fe25519_iszero(const fe25519 *x);
 
 int fe25519_iseq_vartime(const fe25519 *x, const fe25519 *y);
 
diff --git a/src/external/fe25519.c b/src/external/fe25519.c
index 2b0b673e..a7f26c9f 100644
--- a/src/external/fe25519.c
+++ b/src/external/fe25519.c
@@ -120,10 +120,10 @@ void fe25519_pack(unsigned char r[32], const fe25519 *x)
     }
 }
 
-int fe25519_iszero(const fe25519 *x)
+uint32_t fe25519_iszero(const fe25519 *x)
 {
     int i;
-    int r;
+    uint32_t r;
 
     fe25519 t = *x;
     fe25519_freeze(&t);