diff --git a/src/dvd_reader.c b/src/dvd_reader.c

index 4e112d3..e8d50f3 100644

--- a/src/dvd_reader.c

+++ b/src/dvd_reader.c

@@ -1156,13 +1156,13 @@ int InternalUDFReadBlocksRaw( const dvd_reader_t *device, uint32_t lb_number,

   if( !device->dev ) {

     fprintf( stderr, "libdvdread: Fatal error in block read.\n" );

-    return 0;

+    return -1;

   }

   ret = dvdinput_seek( device->dev, (int) lb_number );

   if( ret != (int) lb_number ) {

     fprintf( stderr, "libdvdread: Can't seek to block %u\n", lb_number );

-    return 0;

+    return ret;

   }

   ret = dvdinput_read( device->dev, (char *) data,

diff --git a/src/dvd_udf.c b/src/dvd_udf.c

index 5eb3d2b..68c3a9a 100644

--- a/src/dvd_udf.c

+++ b/src/dvd_udf.c

@@ -516,6 +516,7 @@ static int UDFMapICB( dvd_reader_t *device, struct AD ICB, uint8_t *FileType,

   uint32_t lbnum;

   uint16_t TagID;

   struct icbmap tmpmap;

+  int ret;

   lbnum = partition->Start + ICB.Location;

   tmpmap.lbn = lbnum;

@@ -526,10 +527,16 @@ static int UDFMapICB( dvd_reader_t *device, struct AD ICB, uint8_t *FileType,

   }

   do {

-    if( DVDReadLBUDF( device, lbnum++, 1, LogBlock, 0 ) <= 0 )

+    ret = DVDReadLBUDF( device, lbnum++, 1, LogBlock, 0 );

+    if( ret < 0 ) {

+      return ret;

+    }

+    else if( ret == 0 ) {

       TagID = 0;

-    else

+    }

+    else {

       UDFDescriptor( LogBlock, &TagID );

+    }

     if( TagID == FileEntry ) {

       UDFFileEntry( LogBlock, FileType, partition, File );

@@ -677,6 +688,7 @@ static int UDFGetAVDP( dvd_reader_t *device,

   uint32_t lastsector;

   int terminate;

   struct avdp_t;

+  int ret;

   if(GetUDFCache(device, AVDPCache, 0, avdp))

     return 1;

@@ -687,11 +699,16 @@ static int UDFGetAVDP( dvd_reader_t *device,

   terminate = 0;

   for(;;) {

-    if( DVDReadLBUDF( device, lbnum, 1, Anchor, 0 ) > 0 ) {

-      UDFDescriptor( Anchor, &TagID );

-    } else {

+    ret = DVDReadLBUDF( device, lbnum, 1, Anchor, 0 );

+    if( ret < 0 ) {

+      return ret;

+    }

+    else if( ret == 0 ) {

       TagID = 0;

     }

+    else {

+      UDFDescriptor( Anchor, &TagID );

+    }

     if (TagID != AnchorVolumeDescriptorPointer) {

       /* Not an anchor */

       if( terminate ) return 0; /* Final try failed */

@@ -742,7 +759,7 @@ static int UDFFindPartition( dvd_reader_t *device, int partnum,

   uint8_t *LogBlock = (uint8_t *)(((uintptr_t)LogBlock_base & ~((uintptr_t)2047)) + 2048);

   uint32_t lbnum, MVDS_location, MVDS_length;

   uint16_t TagID;

-  int i, volvalid;

+  int i, volvalid, ret;

   struct avdp_t avdp;

   if(!UDFGetAVDP(device, &avdp))

@@ -761,10 +778,16 @@ static int UDFFindPartition( dvd_reader_t *device, int partnum,

     lbnum = MVDS_location;

     do {

-      if( DVDReadLBUDF( device, lbnum++, 1, LogBlock, 0 ) <= 0 )

+      ret = DVDReadLBUDF( device, lbnum++, 1, LogBlock, 0 );

+      if( ret < 0 ) {

+        return ret;

+      }

+      else if( ret == 0 ) {

         TagID = 0;

-      else

+      }

+      else {

         UDFDescriptor( LogBlock, &TagID );

+      }

       if( ( TagID == PartitionDescriptor ) && ( !part->valid ) ) {

         /* Partition Descriptor */

@@ -805,6 +828,7 @@ uint32_t UDFFindFile( dvd_reader_t *device, const char *filename,

   struct AD RootICB, File, ICB;

   char tokenline[ MAX_UDF_FILE_NAME_LEN ];

   uint8_t filetype;

+  int ret;

   *filesize = 0;

   tokenline[0] = '\0';

@@ -820,10 +844,16 @@ uint32_t UDFFindFile( dvd_reader_t *device, const char *filename,

     /* Find root dir ICB */

     lbnum = partition.Start;

     do {

-      if( DVDReadLBUDF( device, lbnum++, 1, LogBlock, 0 ) <= 0 )

+      ret = DVDReadLBUDF( device, lbnum++, 1, LogBlock, 0 );

+      if( ret < 0 ) {

+        return ret;

+      }

+      else if( ret == 0 ) {

         TagID = 0;

-      else

+      }

+      else {

         UDFDescriptor( LogBlock, &TagID );

+      }

       /* File Set Descriptor */

       if( TagID == FileSetDescriptor )  /* File Set Descriptor */

@@ -886,7 +916,7 @@ static int UDFGetDescriptor( dvd_reader_t *device, int id,

   uint32_t lbnum, MVDS_location, MVDS_length;

   struct avdp_t avdp;

   uint16_t TagID;

-  int i, desc_found = 0;

+  int i, desc_found = 0, ret;

   /* Find Anchor */

   lbnum = 256;   /* Try #1, prime anchor */

   if(bufsize < DVD_VIDEO_LB_LEN)

@@ -904,10 +934,16 @@ static int UDFGetDescriptor( dvd_reader_t *device, int id,

     /* Find  Descriptor */

     lbnum = MVDS_location;

     do {

-      if( DVDReadLBUDF( device, lbnum++, 1, descriptor, 0 ) <= 0 )

+      ret = DVDReadLBUDF( device, lbnum++, 1, descriptor, 0 );

+      if( ret < 0 ) {

+        return ret;

+      }

+      else if( ret == 0 ) {

         TagID = 0;

-      else

+      }

+      else {

         UDFDescriptor( descriptor, &TagID );

+      }

       if( (TagID == id) && ( !desc_found ) )

         /* Descriptor */

         desc_found = 1;