diff --git a/Makefile b/Makefile
index 32d1399..27d4ad0 100644
--- a/Makefile
+++ b/Makefile
@@ -4,6 +4,8 @@ all: $(NAME)
 
 .INCLUDE: "Make.engine"
 
+CFLAGS=-D ABCALC_GSOS
+
 $(NAME): fixtype $(OBJS)
 	occ -o $(NAME) $(OBJS)
 
@@ -19,4 +21,4 @@ fixtype:
 	chtyp -l CC ops/*.c ops/*.h
 
 %.o: %.c
-	occ -c $<
+	occ $(CFLAGS) -c $<
diff --git a/ops/.abCOp.c.swp b/ops/.abCOp.c.swp
new file mode 100644
index 0000000..9dc7471
Binary files /dev/null and b/ops/.abCOp.c.swp differ
diff --git a/ops/abCOp.c b/ops/abCOp.c
index 6dd01b2..0299dcb 100644
--- a/ops/abCOp.c
+++ b/ops/abCOp.c
@@ -92,7 +92,11 @@ abCalcOp *abCalcOpLookup(char *name)
     int i;
 
     for (i = 0; i < gNumOps; i++) {
-        if (strcmp(gOps[i].name, name) == 0) {
+#ifdef ABCALC_GSOS
+        if (stricmp(gOps[i].name, name) == 0) {
+#else
+        if (strcasecmp(gOps[i].name, name) == 0) {
+#endif
             return &gOps[i];
         }
     }