diff --git a/VERSION b/VERSION
index 70b3b850..7df9552c 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-8.3.159
+8.3.160
diff --git a/calma/CalmaRdcl.c b/calma/CalmaRdcl.c
index 9a379599..5f9dbae8 100644
--- a/calma/CalmaRdcl.c
+++ b/calma/CalmaRdcl.c
@@ -55,6 +55,7 @@ extern HashTable calmaDefInitHash;
 /* forward declarations */
 int  calmaElementSref();
 bool calmaParseElement();
+void calmaUniqueCell();
 
 /* Structure used when flattening the GDS hierarchy on read-in */
 
@@ -349,6 +350,7 @@ calmaParseStructure(filename)
 	    freeMagic(newname);
 	}
     }
+    if (CalmaUnique) calmaUniqueCell(strname);	/* Ensure uniqueness */
     cifReadCellDef = calmaFindCell(strname, &was_called, &predefined);
 
     if (predefined == TRUE)
@@ -1136,6 +1138,62 @@ gdsCopyPaintFunc(tile, gdsCopyRec)
     return 0;
 }
 
+/*
+ * ----------------------------------------------------------------------------
+ *
+ * calmaUniqueCell --
+ *
+ *	Attempt to find a cell in the GDS subcell name hash table.
+ *	If one exists, rename its definition so that it will not
+ *	be overwritten when the cell is redefined.
+ *
+ * Results:
+ *	None.
+ *
+ * Side effects:
+ *	None.
+ *
+ * ----------------------------------------------------------------------------
+ */
+
+void
+calmaUniqueCell(sname)
+    char *sname;
+{
+    HashEntry *h;
+    CellDef *def, *testdef;
+    char *newname;
+    int snum = 0;
+
+    h = HashLookOnly(&CifCellTable, sname);
+    if ((h == NULL) || HashGetValue(h) == 0) return;
+
+    def = DBCellLookDef(sname);
+    if (def == (CellDef *)NULL)
+	return;
+
+    /* Cell may have been called but not yet defined---this is okay. */
+    else if ((def->cd_flags & CDAVAILABLE) == 0)
+        return;
+
+    testdef = def;
+    newname = (char *)mallocMagic(10 + strlen(sname));
+     
+    while (testdef != NULL)
+    {
+	/* Keep appending suffix indexes until we find one not used */
+	sprintf(newname, "%s_%d", sname, ++snum);
+	testdef = DBCellLookDef(newname);
+    }
+    DBCellRenameDef(def, newname);
+
+    h = HashFind(&CifCellTable, (char *)sname);
+    HashSetValue(h, 0);
+
+    CalmaReadError("Warning: cell definition \"%s\" reused.\n", sname);
+    freeMagic(newname);
+}
+
 /*
  * ----------------------------------------------------------------------------
  *
diff --git a/calma/CalmaRead.c b/calma/CalmaRead.c
index 7daed818..9857f8d0 100644
--- a/calma/CalmaRead.c
+++ b/calma/CalmaRead.c
@@ -87,6 +87,12 @@ bool CalmaNoDuplicates = FALSE;		/* If TRUE, then if a cell exists in
 					 * in the GDS file, then the cell in
 					 * the GDS file is skipped.
 					 */
+bool CalmaUnique = FALSE;		/* If TRUE, then if a cell exists in
+					 * memory with the same name as a cell
+					 * in the GDS file, then the cell in
+					 * memory is renamed to a unique
+					 * identifier with a _N suffix.
+					 */
 extern void calmaUnexpected();
 extern int calmaWriteInitFunc();
 
diff --git a/calma/calma.h b/calma/calma.h
index d37d50f3..de0314f1 100644
--- a/calma/calma.h
+++ b/calma/calma.h
@@ -33,6 +33,7 @@ extern bool CalmaDoLower;
 extern bool CalmaAddendum;
 extern bool CalmaNoDuplicates;
 extern bool CalmaNoDateStamp;
+extern bool CalmaUnique;
 extern bool CalmaMergeTiles;
 extern bool CalmaFlattenArrays;
 extern bool CalmaNoDRCCheck;
diff --git a/commands/CmdCD.c b/commands/CmdCD.c
index f4034a54..1ba9e472 100644
--- a/commands/CmdCD.c
+++ b/commands/CmdCD.c
@@ -110,6 +110,7 @@ bool cmdDumpParseArgs();
 #define CALMA_POLYS	19
 #define CALMA_PATHS	20
 #define CALMA_UNDEFINED	21
+#define CALMA_UNIQUE	22
 
 #define CALMA_WARN_HELP CIF_WARN_END	/* undefined by CIF module */
 
@@ -160,6 +161,7 @@ CmdCalma(w, cmd)
 	"		put wire paths into individual subcells",
 	"undefined [allow|disallow]\n"
 	"		[dis]allow writing of GDS with calls to undefined cells",
+	"unique [yes|no]	rename any cells with names duplicated in the GDS",
 	NULL
     };
 
@@ -599,6 +601,26 @@ CmdCalma(w, cmd)
 	    CalmaNoDuplicates = (option < 4) ? FALSE : TRUE;
 	    return;
 
+	case CALMA_UNIQUE:
+	    if (cmd->tx_argc == 2)
+	    {
+#ifdef MAGIC_WRAPPER
+		Tcl_SetObjResult(magicinterp, Tcl_NewBooleanObj(CalmaUnique));
+#else
+		TxPrintf("Cell defs that exist before reading GDS will be renamed.\n",
+			(CalmaUnique) ?  "not " : "");
+#endif
+		return;
+	    }
+	    else if (cmd->tx_argc != 3)
+		goto wrongNumArgs;
+
+	    option = Lookup(cmd->tx_argv[2], cmdCalmaYesNo);
+	    if (option < 0)
+		goto wrongNumArgs;
+	    CalmaUnique = (option < 4) ? FALSE : TRUE;
+	    return;
+
 	case CALMA_NO_STAMP:
 	    if (cmd->tx_argc == 2)
 	    {