diff --git a/src/api/pdfrenderer.cpp b/src/api/pdfrenderer.cpp
index 79ba1493..9d5034e3 100644
--- a/src/api/pdfrenderer.cpp
+++ b/src/api/pdfrenderer.cpp
@@ -721,7 +721,12 @@ bool TessPDFRenderer::imageToPDFObj(Pix *pix,
   } else {
     switch (cid->spp) {
       case 1:
-        colorspace.str("  /ColorSpace /DeviceGray\n");
+        if (cid->bps == 1) {
+          colorspace.str("  /ColorSpace /DeviceGray\n"
+                         "  /Decode [1 0]\n");
+        } else {
+          colorspace.str("  /ColorSpace /DeviceGray\n");
+        }
         break;
       case 3:
         colorspace.str("  /ColorSpace /DeviceRGB\n");