diff --git a/doc/geos.sgml b/doc/geos.sgml
index 11ff9c534..f7943f8cd 100644
--- a/doc/geos.sgml
+++ b/doc/geos.sgml
@@ -205,7 +205,7 @@ see them together in the filling box in GeoPaint.
 
 <sect2>GraphicsString
 <p>
-<tt/void GraphicsString (char *myGString)/
+<tt/void GraphicsString (const void *myGString)/
 <p>
 One of the more powerfull routines of GEOS. This function calls other graphic functions depending
 on the given command string. See the structures chapter for a more detailed description.
diff --git a/include/geos/ggraph.h b/include/geos/ggraph.h
index ec9fb0fa1..b550d6ca1 100644
--- a/include/geos/ggraph.h
+++ b/include/geos/ggraph.h
@@ -43,7 +43,7 @@ void __fastcall__ BitOtherClip(void *proc1, void *proc2, char skipl,
                                char skipr, unsigned skiptop,
                                struct iconpic *myIcon);
 
-void __fastcall__ GraphicsString(char *myGfxString);
+void __fastcall__ GraphicsString(const void *myGfxString);
 
 #ifdef __GEOS_CBM__
 void SetNewMode(void);
diff --git a/libsrc/geos-common/graph/graphicsstring.s b/libsrc/geos-common/graph/graphicsstring.s
index 86c74f1a6..282649284 100644
--- a/libsrc/geos-common/graph/graphicsstring.s
+++ b/libsrc/geos-common/graph/graphicsstring.s
@@ -3,7 +3,7 @@
 ;
 ; 25.12.99
 
-; void GraphicsString         (char *myString);
+; void GraphicsString         (const void *myString);
 
             .export _GraphicsString