diff --git a/apache2/re_operators.c b/apache2/re_operators.c
index 3d499b41..0a15e11d 100644
--- a/apache2/re_operators.c
+++ b/apache2/re_operators.c
@@ -464,8 +464,10 @@ static int msre_op_rsub_execute(modsec_rec *msr, msre_rule *rule, msre_var *var,
         msr->of_stream_changed = 1;
 
         msr->stream_output_data = (char *)stream_output_data;
-        if(msr->stream_output_data != NULL)
-            apr_cpystrn(msr->stream_output_data, data, size);
+        if(msr->stream_output_data != NULL) {
+            strncpy(msr->stream_output_data, data, size);
+            msr->stream_output_data[size] = '\0';
+        }
 
     }
 
@@ -485,8 +487,10 @@ static int msre_op_rsub_execute(modsec_rec *msr, msre_rule *rule, msre_var *var,
         msr->if_stream_changed = 1;
 
         msr->stream_input_data = (char *)stream_input_data;
-        if(msr->stream_input_data != NULL)
-            apr_cpystrn(msr->stream_input_data, data, size);
+        if(msr->stream_input_data != NULL)  {
+            strncpy(msr->stream_input_data, data, size);
+            msr->stream_input_data[size] = '\0';
+        }
     }
 
     if (! *error_msg) {