diff --git a/tests/src/helpers.c b/tests/src/helpers.c
index 358f3e4..063ebcd 100644
--- a/tests/src/helpers.c
+++ b/tests/src/helpers.c
@@ -100,7 +100,7 @@
     }
 }
 
-unsigned char *zero_alloc( size_t len )
+unsigned char *mbedtls_test_zero_alloc( size_t len )
 {
     void *p;
     size_t actual_len = ( len != 0 ) ? len : 1;
@@ -120,7 +120,7 @@
     *olen = strlen( ibuf ) / 2;
 
     if( *olen == 0 )
-        return( zero_alloc( *olen ) );
+        return( mbedtls_test_zero_alloc( *olen ) );
 
     obuf = mbedtls_calloc( 1, *olen );
     TEST_HELPER_ASSERT( obuf != NULL );