diff --git a/rtl/amicommon/paramhandling.inc b/rtl/amicommon/paramhandling.inc
index f71e27aaf0..3b9ea03eea 100644
--- a/rtl/amicommon/paramhandling.inc
+++ b/rtl/amicommon/paramhandling.inc
@@ -116,7 +116,7 @@ begin
   Count := 0;
   { first index is one }
   LocalIndex := 1;
-  while (P[Count] <> #0) do
+  while assigned(P) and (P[Count] <> #0) do
   begin
     while (p[count]=' ') or (p[count]=#9) or (p[count]=LineEnding) do
       Inc(count);