diff --git a/lib_com/options.h b/lib_com/options.h
old mode 100644
new mode 100755
index 73c25a9c74d48ac8221f45cadec544114a3f70bb..d295cb628e1b86405030486599bee8b1ee4963fa
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -155,6 +155,7 @@
 #define SBA_AND_OBJECTS
 #ifdef SBA_AND_OBJECTS
 #define OSBA_BR_SWITCHING
+#define FIX_691_OSBA_NULL_META                          /* FhG: Issue 691: Fix crashes for OSBA with NULL metadata */
 #endif
 
 /*#define SPLIT_REND_WITH_HEAD_ROT*/                    /* Dlb,FhG: Split Rendering contributions 21 and 35 */
diff --git a/lib_dec/ivas_ism_metadata_dec.c b/lib_dec/ivas_ism_metadata_dec.c
index e21566dd244d51dc6953fc3eec0e42ff748ca1e8..587eddd195e43c9c2c727534d02378e0920a3bda 100755
--- a/lib_dec/ivas_ism_metadata_dec.c
+++ b/lib_dec/ivas_ism_metadata_dec.c
@@ -321,7 +321,11 @@ ivas_error ivas_ism_metadata_dec(
         }
 
         /* read ISM_NO_META class signalling */
+#ifdef FIX_691_OSBA_NULL_META
+        if ( ism_mode == ISM_MODE_DISC || ism_mode == ISM_SBA_MODE_DISC )
+#else
         if ( ism_mode == ISM_MODE_DISC )
+#endif
         {
             for ( ch = 0; ch < *nchan_transport; ch++ )
             {
@@ -356,6 +360,9 @@ ivas_error ivas_ism_metadata_dec(
                         }
                     }
                     else
+#endif
+#ifdef FIX_691_OSBA_NULL_META
+                        if ( ism_mode != ISM_SBA_MODE_DISC )
 #endif
                     {
                         if ( null_metadata_flag[ch] )
diff --git a/lib_enc/ivas_ism_metadata_enc.c b/lib_enc/ivas_ism_metadata_enc.c
old mode 100755
new mode 100644
index ac67be6585a3de266e3e53a55d3027fbfedc9ac6..1b608987ae6adec50545cd3795ea2251aa8bcaa6
--- a/lib_enc/ivas_ism_metadata_enc.c
+++ b/lib_enc/ivas_ism_metadata_enc.c
@@ -375,6 +375,60 @@ ivas_error ivas_ism_metadata_enc(
         }
     }
 
+#ifdef FIX_691_OSBA_NULL_META
+    /* write ISM metadata flag (one per object) */
+    for ( ch = 0; ch < nchan_transport; ch++ )
+    {
+#ifdef MASA_AND_OBJECTS
+        if ( ism_mode == ISM_MASA_MODE_DISC || ism_mode == ISM_MASA_MODE_MASA_ONE_OBJ )
+        {
+            /* flags will be written in ivas_masa_encode() */
+            hIsmMeta[ch]->ism_imp = ism_imp[ch];
+            hIsmMeta[ch]->ism_md_null_flag = null_metadata_flag[ch];
+            hIsmMeta[ch]->ism_md_lowrate_flag = lowrate_metadata_flag[ch];
+        }
+        else
+        {
+#endif
+            if ( null_metadata_flag[ch] )
+            {
+                /* signal NULL metadata frame */
+                push_indice( hBstr, IND_ISM_MD_NULL_FLAG, 1, ISM_METADATA_MD_FLAG_BITS );
+
+                /* write the ISM class to ISM_NO_META and again the true ISM class */
+                if ( ism_mode != ISM_SBA_MODE_DISC )
+                {
+                    push_indice( hBstr, IND_ISM_METADATA_FLAG, ISM_NO_META, ISM_METADATA_FLAG_BITS );
+                    push_indice( hBstr, IND_ISM_MD_INACTIVE_FLAG, ism_imp[ch], ISM_METADATA_FLAG_BITS );
+                }
+                else
+                {
+                    push_indice( hBstr, IND_ISM_METADATA_FLAG, ISM_NO_META, 1 );
+                }
+            }
+            else if ( ism_mode != ISM_SBA_MODE_DISC )
+            {
+                push_indice( hBstr, IND_ISM_METADATA_FLAG, ism_imp[ch], ISM_METADATA_FLAG_BITS );
+
+                if ( ism_imp[ch] == ISM_NO_META )
+                {
+                    /* signal low-rate ISM_NO_META frame */
+                    push_indice( hBstr, IND_ISM_MD_NULL_FLAG, 0, ISM_METADATA_MD_FLAG_BITS );
+
+                    /* signal presence of MD in low-rate ISM_NO_META frame */
+                    push_indice( hBstr, IND_ISM_MD_INACTIVE_FLAG, lowrate_metadata_flag[ch], ISM_METADATA_INACTIVE_FLAG_BITS );
+                }
+            }
+            else /*ism_mode == ISM_SBA_MODE_DISC*/
+            {
+                /* all objects are considered active*/
+                push_indice( hBstr, IND_ISM_METADATA_FLAG, 1, 1 );
+            }
+#ifdef MASA_AND_OBJECTS
+        }
+#endif
+    }
+#else
     /* write ISM metadata flag (one per object) */
     for ( ch = 0; ch < nchan_transport; ch++ )
     {
@@ -426,6 +480,8 @@ ivas_error ivas_ism_metadata_enc(
 #endif
     }
 
+#endif
+
 
     if ( ism_metadata_flag_global )
     {
@@ -703,6 +759,13 @@ ivas_error ivas_ism_metadata_enc(
             }
         }
     }
+#ifdef FIX_691_OSBA_NULL_META
+    else if ( ism_mode == ISM_SBA_MODE_DISC )
+    {
+        pop_wmops();
+        return error;
+    }
+#endif
 
 #ifdef MASA_AND_OBJECTS
     /*----------------------------------------------------------------*