diff --git a/VERSION b/VERSION
index 1376da5e..caf43a00 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-8.3.449
+8.3.450
diff --git a/calma/CalmaRead.c b/calma/CalmaRead.c
index 796ad013..d8db3fdf 100644
--- a/calma/CalmaRead.c
+++ b/calma/CalmaRead.c
@@ -114,8 +114,6 @@ extern bool CalmaDoLibrary;		/* Also used by GDS write */
 extern void calmaUnexpected();
 extern int calmaWriteInitFunc();
 
-bool calmaParseUnits();
-
 /*
  * Scaling.
  * Multiply all coordinates by calmaReadScale1, then divide them
@@ -351,6 +349,7 @@ calmaParseUnits()
     double metersPerDBUnit;
     double userUnitsPerDBUnit;
     double cuPerDBUnit;
+    bool compatible;
 
     READRH(nbytes, rtype);
 #ifdef	lint
@@ -369,6 +368,39 @@ calmaParseUnits()
     /* Read meters per database unit */
     if (!calmaReadR8(&metersPerDBUnit)) return (FALSE);
 
+    /* Important!  When CalmaReadOnly is TRUE, then this file will have its
+     * contents output verbatim.  But if the database units don't match,
+     * then it will get output at the wrong scale.  Setting a magnification
+     * factor on the instance when generating output might (?) work.  For
+     * now, prohibiting a GDS read in read-only mode when the database units
+     * don't match.  This forces the user either to reconsider the read-only
+     * status or to rewrite the GDS at a compatible scalefactor.
+     */
+    compatible = TRUE;
+    if (CalmaReadOnly == TRUE)
+    {
+	if (CIFCurStyle->cs_flags & CWF_ANGSTROMS)
+	{
+	    if ((int)(0.5 + metersPerDBUnit * 1e12) != 100)
+	    {
+		CalmaReadError("Incompatible scale factor of %g, must be 1e-10.\n",
+				metersPerDBUnit);
+		TxError("Cannot read this file in read-only mode.\n");
+		return FALSE;
+	    }
+	}
+	else
+	{
+	    if ((int)(0.5 + metersPerDBUnit * 1e11) != 100)
+	    {
+		CalmaReadError("Incompatible scale factor of %g, must be 1e-9.\n",
+				metersPerDBUnit);
+		TxError("Cannot read this file in read-only mode.\n");
+		return FALSE;
+	    }
+	}
+    }
+
 #ifdef	notdef
     TxPrintf("1 database unit equals %e user units\n", userUnitsPerDBUnit);
     TxPrintf("1 database unit equals %e meters\n", metersPerDBUnit);
diff --git a/calma/CalmaWrite.c b/calma/CalmaWrite.c
index a1a2d931..70e027a8 100644
--- a/calma/CalmaWrite.c
+++ b/calma/CalmaWrite.c
@@ -706,7 +706,7 @@ calmaFullDump(def, fi, outf, filename)
 
     static int hdrSkip[] = { CALMA_FORMAT, CALMA_MASK, CALMA_ENDMASKS,
 		CALMA_REFLIBS, CALMA_FONTS, CALMA_ATTRTABLE,
-		CALMA_STYPTABLE, CALMA_GENERATIONS, CALMA_UNITS, -1 };
+		CALMA_STYPTABLE, CALMA_GENERATIONS, -1 };
     static int skipBeforeLib[] = { CALMA_LIBDIRSIZE, CALMA_SRFNAME,
 		CALMA_LIBSECUR, -1 };
 
@@ -722,11 +722,17 @@ calmaFullDump(def, fi, outf, filename)
     calmaSkipSet(skipBeforeLib);
     if (!calmaReadStringRecord(CALMA_LIBNAME, &libname)) goto done;
 
-    // NOTE:  CALMA_UNITS needs to be parsed to determine if units in
-    // the input file are compatible with units being used in the output
-    // file.
     calmaSkipSet(hdrSkip);
 
+    // CALMA_UNITS needs to be parsed to determine if units in the
+    // input file are compatible with units being used in the output
+    // file.
+    if (calmaParseUnits() == FALSE)
+    {
+	TxError("Error:  Library %s has incompatible database units!\n", libname);
+	return;
+    }
+
     // Record the GDS library so it will not be processed again.
     he = HashFind(&calmaLibHash, filename);
     if ((char *)HashGetValue(he) != NULL)
diff --git a/calma/CalmaWriteZ.c b/calma/CalmaWriteZ.c
index 66ef9245..3890ceb7 100644
--- a/calma/CalmaWriteZ.c
+++ b/calma/CalmaWriteZ.c
@@ -682,7 +682,7 @@ calmaFullDumpZ(def, fi, outf, filename)
 
     static int hdrSkip[] = { CALMA_FORMAT, CALMA_MASK, CALMA_ENDMASKS,
 		CALMA_REFLIBS, CALMA_FONTS, CALMA_ATTRTABLE,
-		CALMA_STYPTABLE, CALMA_GENERATIONS, CALMA_UNITS, -1 };
+		CALMA_STYPTABLE, CALMA_GENERATIONS, -1 };
     static int skipBeforeLib[] = { CALMA_LIBDIRSIZE, CALMA_SRFNAME,
 		CALMA_LIBSECUR, -1 };
 
@@ -698,10 +698,14 @@ calmaFullDumpZ(def, fi, outf, filename)
     calmaSkipSet(skipBeforeLib);
     if (!calmaReadStringRecord(CALMA_LIBNAME, &libname)) goto done;
 
-    // NOTE:  CALMA_UNITS needs to be parsed to determine if units in
-    // the input file are compatible with units being used in the output
+    // CALMA_UNITS needs to be parsed to determine if units in the
+    // input file are compatible with units being used in the output
     // file.
-    calmaSkipSet(hdrSkip);
+    if (calmaParseUnits() == FALSE)
+    {
+	TxError("Error:  Library %s has incompatible database units!\n", libname);
+	return;
+    }
 
     // Record the GDS library so it will not be processed again.
     he = HashFind(&calmaLibHash, filename);
diff --git a/calma/calmaInt.h b/calma/calmaInt.h
index 4fb56a2f..fea4fb36 100644
--- a/calma/calmaInt.h
+++ b/calma/calmaInt.h
@@ -237,6 +237,7 @@ extern bool calmaIsContactCell;
 
 extern char *calmaRecordName();
 extern void calmaSkipSet();
+extern bool calmaParseUnits();
 
 extern int compport();