diff --git a/libsrc/geos/memory/cmpfstring.s b/libsrc/geos/memory/cmpfstring.s
index e924febff..15011dcaa 100644
--- a/libsrc/geos/memory/cmpfstring.s
+++ b/libsrc/geos/memory/cmpfstring.s
@@ -4,7 +4,7 @@
 ;
 ; 22.12.99, 29.07.2000
 
-; void CmpFString (char length, char *dest, char* source);
+; char CmpFString (char length, char *dest, char* source);
 
 	    .import DoubleSPop, SetPtrXY
 	    .import popa
@@ -16,4 +16,7 @@ _CmpFString:
 	    jsr DoubleSPop
 	    jsr popa
 	    jsr SetPtrXY
-	    jmp CmpFString
+	    jsr CmpFString
+	    bne L1
+	    jmp return0
+L1:	    jmp return1